Tetra Tech (TTEK) 10-Q2 Feb 242024 Q1 Quarterly reportFinancial data

Company Profile

Cover

Cover - shares	3 Months Ended
Cover - shares	Dec. 31, 2023	Jan. 22, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	0-19655
Entity Registrant Name	TETRA TECH, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	95-4148514
Entity Address, Address Line One	3475 East Foothill Boulevard
Entity Address, City or Town	Pasadena
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91107
City Area Code	626
Local Phone Number	351-4664
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	TTEK
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		53,466,381
Entity Central Index Key	0000831641
Amendment Flag	false
Current Fiscal Year End Date	--09-29
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Current assets:
Cash and cash equivalents	$ 198,689	$ 168,831
Accounts receivable, net	1,040,510	974,535
Contract assets	89,073	113,939
Prepaid expenses and other current assets	125,769	98,719
Total current assets	1,454,041	1,356,024
Property and equipment, net	74,971	74,832
Right-of-use assets, operating leases	179,513	175,932
Goodwill	1,923,146	1,880,244
Intangible assets, net	168,134	173,936
Deferred tax assets	76,210	89,002
Other non-current assets	74,808	70,507
Total assets	3,950,823	3,820,477
Current liabilities:
Accounts payable	207,062	173,271
Accrued compensation	222,686	302,755
Contract liabilities	382,862	335,044
Short-term lease liabilities, operating leases	68,091	65,005
Current contingent earn-out liabilities	37,556	51,108
Other current liabilities	242,738	280,959
Total current liabilities	1,160,995	1,208,142
Deferred tax liabilities	11,620	14,256
Long-term debt	945,319	879,529
Long-term lease liabilities, operating leases	139,537	144,685
Non-current contingent earn-out liabilities	18,048	22,314
Other non-current liabilities	137,617	148,045
Commitments and contingencies (Note 17)
Equity:
Preferred stock - authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at December 31, 2023 and October 1, 2023	0	0
Common stock - authorized, 150,000 shares of $0.01 par value; issued and outstanding, 53,466 and 53,248 shares at December 31, 2023 and October 1, 2023, respectively	534	532
Additional paid-in capital	9,979	0
Accumulated other comprehensive loss	(132,202)	(195,295)
Retained earnings	1,659,295	1,598,196
Tetra Tech stockholders’ equity	1,537,606	1,403,433
Noncontrolling interests	81	73
Total stockholders' equity	1,537,687	1,403,506
Total liabilities and stockholders' equity	$ 3,950,823	$ 3,820,477

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Oct. 01, 2023
Statement of Financial Position [Abstract]
Preferred stock, authorized shares (in shares)	2,000,000	2,000,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, authorized shares (in shares)	150,000,000	150,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	53,466,000	53,248,000
Common stock, shares outstanding (in shares)	53,466,000	53,248,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Revenue	$ 1,228,267	$ 894,766
Gross profit	190,498	153,246
Selling, general and administrative expenses	(79,417)	(56,502)
Acquisition and integration expenses	0	(3,761)
Contingent consideration – fair value adjustments	0	(933)
Income from operations	111,081	92,050
Interest expense, net	(9,577)	(5,372)
Other non-operating income	0	67,995
Income before income tax expense	101,504	154,673
Income tax expense	(26,524)	(37,958)
Net income	74,980	116,715
Net income attributable to noncontrolling interests	(8)	(9)
Net income attributable to Tetra Tech, basic	74,972	116,706
Net income attributable to Tetra Tech, diluted	$ 74,972	$ 116,706
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 1.41	$ 2.20
Diluted (in dollars per share)	$ 1.40	$ 2.18
Weighted-average common shares outstanding:
Basic (in shares)	53,317	53,069
Diluted (in shares)	53,738	53,529
Subcontractor costs
Cost of revenue	$ (213,098)	$ (158,204)
Other costs of revenue
Cost of revenue	$ (824,671)	$ (583,316)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 74,980	$ 116,715
Other comprehensive income, net of tax
Foreign currency translation adjustment, net of tax	63,106	33,107
Gain (loss) on cash flow hedge valuations, net of tax	0	(89)
Net pension adjustments	(13)	0
Other comprehensive income, net of tax	63,093	33,018
Comprehensive income, net of tax	138,073	149,733
Comprehensive income attributable to noncontrolling interests, net of tax	8	9
Comprehensive income attributable to Tetra Tech, net of tax	$ 138,065	$ 149,724

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Cash flows from operating activities:
Net income	$ 74,980	$ 116,715
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,484	6,616
Amortization of stock-based awards	7,641	7,184
Deferred income taxes	(1,624)	15,935
Fair value adjustments to foreign currency forward contract	0	(67,995)
Other non-cash items	123	601
Changes in operating assets and liabilities, net of effects of business acquisitions:
Accounts receivable and contract assets	(22,288)	(16,175)
Prepaid expenses and other assets	(28,615)	5,967
Accounts payable	33,790	3,820
Accrued compensation	(80,069)	(53,201)
Contract liabilities	41,862	27,769
Income taxes receivable/payable	(15,941)	4,387
Other liabilities	(20,097)	(26,432)
Net cash provided by operating activities	9,246	25,191
Cash flows from investing activities:
Capital expenditures	(3,456)	(4,996)
Proceeds from sale of assets	22	51
Net cash used in investing activities	(3,434)	(4,945)
Cash flows from financing activities:
Proceeds from borrowings	125,000	60,889
Repayments on long-term debt	(60,000)	(73,125)
Taxes paid on vested restricted stock	(12,670)	(16,586)
Payments of contingent earn-out liabilities	(18,862)	0
Stock options exercised	335	57
Dividends paid	(13,873)	(12,186)
Principal payments on finance leases	(1,539)	(1,316)
Net cash provided by (used in) financing activities	18,391	(42,267)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	5,655	8,695
Net increase (decrease) in cash, cash equivalents and restricted cash	29,858	(13,326)
Cash, cash equivalents and restricted cash at beginning of period	168,831	185,491
Cash, cash equivalents and restricted cash at end of period	198,689	172,165
Cash paid during the period for:
Interest	9,768	3,433
Income taxes, net of refunds received of $0.9 million and $0.1 million	43,297	14,540
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	198,689	164,397
Restricted cash	0	7,768
Total cash, cash equivalents and restricted cash	$ 198,689	$ 172,165

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Statement of Cash Flows [Abstract]
Income tax refunds	$ 0.9	$ 0.1

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Total Tetra Tech Equity	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Non-Controlling Interests
Beginning balance (in shares) at Oct. 02, 2022			52,981
Beginning balance at Oct. 02, 2022	$ 1,183,137	$ 1,183,087	$ 530	$ 0	$ (208,144)	$ 1,390,701	$ 50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	116,715	116,706				116,706	9
Other comprehensive income (loss)	33,018	33,018			33,018
Cash dividends per common share	(12,186)	(12,186)				(12,186)
Stock-based compensation	7,184	7,184		7,184
Restricted & performance shares released (in shares)			145
Restricted & performance shares released	(16,586)	(16,586)	$ 1	(16,587)
Stock options exercised (in shares)			2
Stock options exercised	57	57	$ 0	57
Shares issued for Employee Stock Purchase Plan (in shares)			98
Shares issued for Employee Stock Purchase Plan	12,628	12,628	$ 1	12,627
Ending balance (in shares) at Jan. 01, 2023			53,226
Ending balance at Jan. 01, 2023	1,323,967	1,323,908	$ 532	3,281	(175,126)	1,495,221	59
Beginning balance (in shares) at Oct. 01, 2023			53,248
Beginning balance at Oct. 01, 2023	1,403,506	1,403,433	$ 532	0	(195,295)	1,598,196	73
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	74,980	74,972				74,972	8
Other comprehensive income (loss)	63,093	63,093			63,093
Cash dividends per common share	(13,873)	(13,873)				(13,873)
Stock-based compensation	7,641	7,641		7,641
Restricted & performance shares released (in shares)			105
Restricted & performance shares released	(12,670)	(12,670)	$ 1	(12,671)
Stock options exercised (in shares)			9
Stock options exercised	335	335	$ 0	335
Shares issued for Employee Stock Purchase Plan (in shares)			104
Shares issued for Employee Stock Purchase Plan	14,675	14,675	$ 1	14,674
Ending balance (in shares) at Dec. 31, 2023			53,466
Ending balance at Dec. 31, 2023	$ 1,537,687	$ 1,537,606	$ 534	$ 9,979	$ (132,202)	$ 1,659,295	$ 81

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares			3 Months Ended
	Dec. 13, 2023	Dec. 09, 2022	Dec. 31, 2023	Jan. 01, 2023
Statement of Stockholders' Equity [Abstract]
Dividend paid per share (in dollars per share)	$ 0.26	$ 0.23	$ 0.26	$ 0.23

Basis of Presentation

Basis of Presentation	3 Months Ended
Basis of Presentation	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements and related notes of Tetra Tech, Inc. (“we,” “us,” “our” or "Tetra Tech") have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. They do not include all of the information and footnotes required by U.S. GAAP for complete financial statements and, therefore, should be read in conjunction with the audited consolidated financial statements and the notes contained in our Annual Report on Form 10-K for the fiscal year ended October 1, 2023. These financial statements reflect all normal recurring adjustments that are considered necessary for a fair statement of our financial position, results of operations and cash flows for the interim periods presented. The results of operations and cash flows for any interim period are not necessarily indicative of results for the full fiscal year or for future fiscal yea rs. Certain prior year amounts have been reclassified to conform to the current year presentation in the accompanying notes.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
Recent Accounting Pronouncements	Dec. 31, 2023
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2021, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2021-10, Government Assistance (Topic 832) , which requires annual disclosures for transactions with a government authority that are accounted for by applying a grant or contribution model by analogy, including (1) the types of transactions, (2) the accounting for those transactions, and (3) the effect of those transactions on an entity's financial statements. ASU 2021-10 was effective for us beginning in the first quarter of fiscal 2023. In fiscal 2020, the Canadian federal government implemented the Canadian Emergency Wage Subsidy ("CEWS") program in response to the negative impact of the coronavirus disease 2019 pandemic on businesses operating in Canada. Some of our Canadian legal entities qualified for and applied for these CEWS cash benefits to partially offset the impacts of revenue reductions and on-going staffing costs. The $21 million total received was initially recorded in "Other long-term liabilities" until all potential amendments to the qualification criteria, including some that were proposed with retroactive application, were finalized in fiscal 2022. In the first quarter of fiscal 2024, we distributed approximately $10 million to our Canadian employees. The remaining $11 million, which we expect to distribute within one year, is reported in "Accrued compensation". We do not expect there will be any related impact on our operating income, and we have no outstanding applications for further government assistance. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires that an entity report segment information in accordance with Topic 280, Segment Reporting. The amendments in the ASU are intended to improve reportable segment disclosure requirements primarily through enhanced disclosures about significant segment expenses. The amendments in this ASU are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 (fiscal 2025 for us). Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which requires that an entity, on an annual basis, disclose additional income tax information, primarily related to the rate reconciliation and income taxes paid. The amendments in the ASU are intended to enhance the transparency and decision usefulness of income tax disclosures. The amendments in this ASU are effective for annual periods beginning after December 15, 2024 (fiscal 2026 for us). Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements; however, we do not plan to adopt Topic 740 before fiscal 2026.

Revenue and Contract Balances

Revenue and Contract Balances	3 Months Ended
Revenue and Contract Balances	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue and Contract Balances	Revenue and Contract Balances We disaggregate revenue by client sector and contract type, as we believe it best depicts how the nature, timing and uncertainty of revenue and cash flows are affected by economic factors. The following tables present revenue disaggregated by client sector and contract type (in thousands): Three Months Ended December 31, January 1, Client Sector: U.S. federal government (1) $ 382,076 $ 276,075 U.S. state and local government 150,925 153,195 U.S. commercial 222,430 198,956 International (2) 472,836 266,540 Total $ 1,228,267 $ 894,766 Contract Type: Fixed-price $ 471,442 $ 327,737 Time-and-materials 549,651 420,570 Cost-plus 207,174 146,459 Total $ 1,228,267 $ 894,766 (1) Includes revenue generated under U.S. federal government contracts performed outside the United States. (2) Includes revenue generated from non-U.S. clien ts, primarily in Canada, Australia, Europe and the United Kingdom. Other than the U.S. federal government, no single client accounted for more than 10% of our revenue for the first quarters of fiscal 2024 and 2023. Contract Assets and Contract Liabilities We invoice customers based on the contractual terms of each contract. However, the timing of revenue recognition may differ from the timing of invoice issuance. Contract assets represent revenue recognized in excess of the amounts for which we have the contractual right to bill our customers. Such amounts are recoverable from customers based upon various measures of performance, including achievement of certain milestones or completion of a contract. In addition, many of our time and materials arrangements are billed in arrears pursuant to contract terms that are standard within the industry, resulting in contract assets and/or unbilled receivables being recorded, as revenue is recognized in advance of billings. Contract retentions, included in contract assets, represent amounts withheld by clients until certain conditions are met or the project is completed, which may extend beyond one year. Contract liabilities consist of billings in excess of revenue recognized. Contract liabilities decrease as we recognize revenue from the satisfaction of the related performance obligation and increase as billings in advance of revenue recognition occur. Contract assets and liabilities are reported in a net position on a contract-by-contract basis at the end of each reporting period. There were no substantial non-current contract assets or liabilities for the periods presented. Net contract assets/liabilities consisted of the following (in thousands): Balance at December 31, October 1, 2023 Contract assets (1) $ 89,073 $ 113,939 Contract liabilities 382,862 335,044 Net contract liabilities $ (293,789) $ (221,105) (1) Inclu des $6.0 million and $6.8 million of contract retentions at December 31, 2023 and October 1, 2023, respectively. In the first quarters of fiscal 2024 and 2023, we recognized revenue of approximately $130 million and $81 million, respectively, from the amounts included in the contract liability balances at the end of fiscal 2023 and 2022, respectively. Revenue is recognized by measuring progress over time under Accounting Standards Codification Topic 606, "Revenue from Contracts with Customers". We estimate and measure progress on our contracts over time whereby we compare our total costs incurred on each contract as a percentage of the total expected contract costs. Changes in those estimates could result in the recognition of cumulative catch-up adjustments to the contract’s inception-to-date revenue, costs and profit in the period in which such changes are made. As a result, in the first quarters of fiscal 2024 and 2023, we recognized net favorable revenue and operating income adjustments of $5.7 million and $3.5 million, respectively. C hanges in revenue and cost estimates could also result in a projected loss, determined at the contract level, which would be recorded immediate ly in earnings. At December 31, 2023 and October 1, 2023, our consolidated balance sheets included liabilities for anticipated losses of $9.2 million and $8.5 million, respectively. The estimated cost to complete these related contracts was approximately $68 million at December 31, 2023 and October 1, 2023. Accounts Receivable, Net Net accounts receivable consisted of the following (in thousands): Balance at December 31, October 1, Billed $ 700,880 $ 672,712 Unbilled 344,628 306,788 Total accounts receivable 1,045,508 979,500 Allowance for doubtful accounts (4,998) (4,965) Total accounts receivable, net $ 1,040,510 $ 974,535 Billed accounts receivable represent amounts billed to clients that have not been collected. Unbilled accounts receivable, which represent an unconditional right to payment subject only to the passage of time, include unbilled amounts typically resulting from revenue recognized but not yet billed pursuant to contract terms or billed after the period end date. Substantially all of our unbilled receivables at December 31, 2023 are expected to be billed and collecte d within 12 months. The allowance for doubtful accounts represents amounts that are expected to become uncollectible or unrealizable in the future. We determine an estimated allowance for uncollectible accounts based on management's consideration of trends in the actual and forecasted credit quality of our clients, including delinquency and payment history; type of client, such as a government agency or a commerci al sector client; and general economic and industry conditions , which may affect our clients' ability to pay . Other than the U.S. federal government, no single client accounted for more than 10% of our accounts receivable at December 31, 2023 and October 1, 2023. Remaining Unsatisfied Performance Obligations (“RUPO”) Our RUPO represents a measure of the total dollar value of work to be performed on contracts awarded and in progress. We had $4.7 billion of RUPO at December 31, 2023. RUPO increases with awards from new contracts or additions on existing contracts, and decreases as work is performed and revenue is recognized on existing contracts. RUPO may also decrease when projects are canceled or modified in scope. We include a contract within our RUPO when the contract is awarded and an agreement on contract terms has been reached. We expect to satisfy our RUPO at December 31, 2023 over the following periods (in thousands): Amount Within 12 months $ 3,149,015 Beyond 1,558,073 Total $ 4,707,088

Acquisitions

Acquisitions	3 Months Ended
Acquisitions	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Acquisitions	Acquisitions On September 23, 2022, we made an all cash offer to acquire all of the outstanding shares of RPS Group plc ("RPS"), a publicly traded company on the London Stock Exchange for 222 pence per share, through a scheme of arrangement, which was unanimously recommended by RPS' Board of Directors. On November 3, 2022, RPS' shareholders approved the scheme of arrangement. On January 19, 2023, the court-sanctioned scheme of arrangement to purchase RPS was approved, and we completed the acquisition on January 23, 2023. RPS employs approximately 5,000 associates in the United Kingdom, Europe, Asia Pacific and North America, delivering high-end solutions, especially in energy transformation, water and program management for government and commercial clients. Substantially all of RPS is included in our Commercial/International Services Group ("CIG") segment. The total purchase price of RPS was approximately £633 million ($784 million). In connection with the transaction, we incurred acquisition and integration costs of $33.2 million, primarily for professional fees, substantially all of which were paid as of fiscal 2023 year-end. On January 23, 2023, we also settled a foreign exchange forward contract that was integral to our plan to finance the RPS acquisition. The cash gain of $109.3 million did not qualify for hedge accounting. As a result, the gain was recognized as non-operating income over the life of the contract and not included in the purchase price allocation below. However, the cash proceeds of $109.3 million economically reduced the purchase price for the shares of RPS to approximately $675 million. This forward contract is explained further in Note 15, "Derivative Financial Instruments". The table below represents the purchase price allocation for RPS based on estimates, assumptions, valuations and other analyses as of January 23, 2023. The purchase consideration, excluding the aforementioned forward contract gain, was allocated to the tangible and intangible assets, and liabilities of RPS based on their estimated fair values, with any excess purchase consideration allocated to goodwill as follows (in thousands): Amount Cash and cash equivalents $ 32,093 Accounts receivable and contract assets 202,303 Prepaid expenses and other current assets 45,999 Income taxes receivables 1,999 Property and equipment 38,435 Right-of-use assets, operating leases 40,179 Intangible assets 174,094 Deferred income taxes 35,084 Other long-term assets 1,061 Total assets acquired 571,247 Accounts payable $ (44,376) Accrued compensation (19,073) Contract liabilities (46,287) Income tax payable (7,083) Short-term lease liabilities, operating leases (13,477) Other current liabilities (135,474) Current portion of long-term debt (91,973) Long-term lease liabilities, operating leases (26,702) Other long-term liabilities (13,742) Deferred tax liabilities (41,613) Total liabilities assumed (439,800) Fair value of net assets acquired 131,447 Goodwill 652,762 Total purchase consideration $ 784,209 The following table summarizes the estimated fair values that were assigned to intangible assets at the acquisition date: Fair Value Weighted-Average Estimated Useful Life (in thousands) (in years) Backlog $ 27,880 1.6 Trade names 27,260 3.0 Client relations 118,954 11.1 Total intangible assets acquired $ 174,094 8.3 Estimated fair value measurements for the intangible assets related to the RPS acquisition were made using Level 3 inputs including discounted cash flow techniques. Fair value was estimated using a multi-period excess earnings method for backlog and client relations and a relief from royalty method for trade names. The significant assumptions used in estimating fair value of backlog and client relations include (i) the estimated life the asset will contribute to cash flows, such as remaining contractual terms, (ii) revenue growth rates and EBITDA margins, (iii) attrition rate of customers, and (iv) the estimated discount rates that reflect the level of risk associated with receiving future cash flows. The significant assumptions used in estimating fair value of trade names include the royalty rates and discount rates. Supplemental Pro Forma Information (Unaudited) Following are the supplemental consolidated financial results of Tetra Tech and RPS for the first quarter of fiscal 2023 on an unaudited pro forma basis, as if the RPS acquisition had been consummated as of the beginning of fiscal 2022 (in thousands): Three Months Ended January 1, Revenue $ 1,107,301 Net Income including noncontrolling interests $ 63,701 In fiscal 2023, we also acquired Amyx, Inc. (“Amyx”), an enterprise technology services, cybersecurity and management consulting firm based in Reston, Virginia. With over 500 employees, Amyx provides application modernization, cybersecurity, systems engineering, financial management and program management support on over 30 Federal Government programs. Amyx is included in our Government Services Group (" GSG") segment. The total fair value of the purchase price of Amyx was $120.9 million, comprised of a $100.0 million payable in a promissory note issued to the sellers (paid subsequent to closing), $8.7 million of payables related to estimated post-closing adjustments, and $12.2 million for the estimated fair value of contingent earn-out obligations, with a maximum of $25.0 million, based upon the achievement of specified operating income targets in each of the three years following the acquisition date. Amyx was not considered significant to our consolidated financial statements. As a result, no pro forma information has been provided. The majority of the goodwill from the fiscal 2023 acquisitions is not deductible for tax purposes. The results of fiscal 2023 acquisitions were included in our consolidated financial statements beginning on the respective closing dates. Goodwill additions resulting from the fiscal 2023 business combinations are primarily attributable to the significant technical expertise residing in embedded workforces that are sought out by clients, synergies expected to arise after the acquisitions in the areas of enterprise technology services, data management, energy transformation, water, program management, and data analytics and the long-standing reputations of RPS and Amyx. These acquisitions further expand and complement our market-leading positions in water, renewable energy and sustainable infrastructure; enhanced by a combined suite of differentiated data analytics and digital technologies, and expansion into existing and new geographies. Intangible assets with finite lives arise from business acquisitions and are amortized based on the period over which the contractual or economic benefit of the intangible assets are expected to be realized on a straight-line basis over the useful lives of the underlying assets, ranging from one Most of our acquisition agreements include contingent earn-out agreements, which are generally based on the achievement of future operating income thresholds. The contingent earn-out arrangements are based on our valuations of the acquired companies and reduce the risk of overpaying for acquisitions if the projected financial results are not achieved. The fair values of any earn-out arrangements are included as part of the purchase price of the acquired companies on their respective acquisition dates. For each transaction, we estimate the fair value of contingent earn-out payments as part of the initial purchase price and record the estimated fair value of contingent consideration as a liability in “Current contingent earn-out liabilities” and “Non-current contingent earn-out liabilities” on the consolidated balance sheets. We consider several factors when determining that contingent earn-out liabilities are part of the purchase price, including the following: (1) the valuation of our acquisitions is not supported solely by the initial consideration paid, and the contingent earn-out formula is a critical and material component of the valuation approach to determining the purchase price; and (2) the former owners of acquired companies that remain as key employees receive compensation other than contingent earn-out payments at a reasonable level compared with the compensation of our other key employees. The contingent earn-out payments are not affected by employment termination. We measure our contingent earn-out liabilities at fair value on a recurring basis using significant unobservable inputs classified within Level 3 of the fair value hierarchy. We use a probability-weighted discounted income approach as a valuation technique to convert future estimated cash flows to a single present value amount. The significant unobservable inputs used in the fair value measurements are operating income projections over the earn-out period (generally three We review and reassess the estimated fair value of contingent consideration on a quarterly basis, and the updated fair value could differ materially from the initial estimates. Changes in the estimated fair value of our contingent earn-out liabilities related to the time component of the present value calculation are reported in interest expense. Adjustments to the estimated fair value related to changes in all other unobservable inputs are reported in operating incom e. In the first quarter of fiscal 2024, we evaluated our estimates for contingent consideration liabilities for the remaining earn-out periods for each individual acquisition, which included a review of their financial results to-date, the status of ongoing projects in their RUPO, and the inventory of prospective new contract awards. For the first quarters of fiscal 2024 and 2023, we had no material adjustments to our contingent earn-out liabilities in operating income. The following table summarizes the changes in the fair value of estimated contingent consideration for the first quarters of fiscal 2024 and 2023 (in thousands): Three Months Ended December 31, January 1, Beginning balance $ 73,422 $ 65,566 Payments of contingent consideration (18,862) — Adjustments to fair value recorded in earnings (37) 933 Interest accretion expense 471 513 Effect of foreign currency exchange rate changes 610 2,017 Ending balance $ 55,604 $ 69,029 Maximum potential payout at end of period $ 92,253 $ 120,882

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
Goodwill and Intangible Assets	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The following table summarizes the changes in the carrying value of goodwill by reportable segment (in thousands): GSG CIG Total Balance at October 1, 2023 $ 659,942 $ 1,220,302 $ 1,880,244 Translation adjustments 2,731 40,171 42,902 Balance at December 31, 2023 $ 662,673 $ 1,260,473 $ 1,923,146 The foreign currency translation adjustments resulted from our foreign subsidiaries with functional currencies that are different than our reporting currency. These goodwill amounts are presented net of reductions from historical impairment adjustments. The gross amounts for GSG were $680.4 million and $677.6 million at December 31, 2023 and October 1, 2023, respectively, excluding accumulated impairment of $17.7 million at each date. The gross amounts of goodwill for CIG were $1,381.9 million and $1,341.8 million at December 31, 2023 and October 1, 2023, respectively, excluding accumulated impairment of $121.5 million at each date. We perform our annual goodwill impairment review at the beginning of our fiscal fourth quarter. Our most recent annual review at July 3, 2023 (i.e. the first day of our fourth quarter in fiscal 2023) indicated that we had no impairment of goodwill, and all of our reporting units had estimated fair values that were in excess of their carrying values, including goodwill. At July 3, 2023, and after the reallocation of goodwill on the first day of fiscal 2023, we had no reporting units that had estimated fair values that exceeded their carrying val ues by less than 45%. We also regularly evaluate whether events and circumstances have occurred that may indicate a potential change in the recoverability of goodwill. We perform interim goodwill impairment reviews between our annual reviews if certain events and circumstances have occurred, such as a deterioration in general economic conditions; an increase in the competitive environment; a change in management, key personnel, strategy or customers; negative or declining cash flows; or a decline in actual or planned revenue or earnings compared with actual and projected results of relevant prior periods. Although we believe that our estimates of fair value for these reporting units are reasonable, if financial performance for these reporting units falls significantly below our expectations or market prices for similar business decline, the goodwill for these reporting units could become impaired. The following table presents the gross amount and accumulated amortization of our acquired identifiable intangible assets with finite useful lives included in “Intangible assets, net” on the consolidated balance sheets ($ in thousands): Period Ended December 31, 2023 October 1, 2023 Weighted- Gross Accumulated Net Amount Gross Accumulated Net Amount Client relations 9.2 $ 175,486 $ (41,572) $ 133,914 $ 169,217 $ (36,072) $ 133,145 Backlog 0.8 66,052 (54,960) 11,092 63,825 (47,802) 16,023 Trade names 2.1 39,084 (15,956) 23,128 37,411 (12,643) 24,768 Total $ 280,622 $ (112,488) $ 168,134 $ 270,453 $ (96,517) $ 173,936 Amortization expense for the three months e nded December 31, 2023 w as $12.5 million, compared to $3.4 million for the prior-year periods. Estimated amortization expense for the remainder of fiscal 2024 and succeeding years is as follows (in thousands): Amount 2024 (remaining) $ 31,021 2025 29,138 2026 20,563 2027 14,440 2028 13,930 Beyond 59,042 Total $ 168,134

Property and Equipment

Property and Equipment	3 Months Ended
Property and Equipment	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following (in thousands): Balance at December 31, October 1, Equipment, furniture and fixtures $ 136,873 $ 132,744 Leasehold improvements 40,942 44,733 Total property and equipment 177,815 177,477 Accumulated depreciation (102,844) (102,645) Property and equipment, net $ 74,971 $ 74,832 The depreciation expense related to property and equipment

Stock Repurchase and Dividends

Stock Repurchase and Dividends	3 Months Ended
Stock Repurchase and Dividends	Dec. 31, 2023
Stock Repurchase And Dividends [Abstract]
Stock Repurchase and Dividends	Stock Repurchase and Dividends On October 5, 2021, our Board of Directors authorized a new stock repurchase program under which we could repurchase up to $400 million of our common stock . We did not repurchase any shares of our common stock in the first quarters of fiscal 2024 and 2023. At December 31, 2023, we had a remaining balance of $347.8 million under our stock repurchase program. The following table presents dividends declared and paid in the first quarters of fis cal 2024 and 2023: Declare Date Dividend Paid Per Share Record Date Payment Date Dividend Paid November 13, 2023 $ 0.26 November 30, 2023 December 13, 2023 $ 13,873 November 7, 2022 $ 0.23 November 21, 2022 December 9, 2022 $ 12,186 Subsequent Event. On January 29, 2024, our Board of Directors declared a quarterly cash dividend of $0.26 per share payable on February 27, 2024 to stockholders of record as of the close of business on February 14, 2024.

Leases

Leases	3 Months Ended
Leases	Dec. 31, 2023
Leases [Abstract]
Leases	Leases Our operating leases are primarily for corporate and project office spaces. To a much lesser extent, we have operating leases for vehicles and equipment. Our operating leases have remaining lease terms of one month to ten years, some of which may include options to extend the leases for up to five years. We determine if an arrangement is a lease at inception. Operating leases are included in "Right-of-use assets, operating leases", "Short-term lease liabilities, operating leases" and "Long-term lease liabilities, operating leases" in the consolidated balance sheets. Our finance leases are primarily for certain IT equipment. Our finance leases are immaterial. Right-of-use ("ROU") assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, incremental borrowing rates are used based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset at the commencement date also includes any lease payments made to the lessor at or before the commencement date and initial direct costs less lease incentives received. Lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. The components of lease costs are as follows (in thousands): Three Months Ended December 31, January 1, Operating lease cost $ 24,232 $ 20,961 Sublease (income) cost (57) (32) Total lease cost $ 24,175 $ 20,929 Supplemental cash flow information related to leases is as follows (in thousands): Three Months Ended December 31, January 1, Operating cash flows for operating leases $ 19,682 $ 16,493 Right-of-use assets obtained in exchange for new operating lease liabilities 9,803 11,117 Supplemental balance sheet and other information related to leases are as follows (in thousands): Balance at December 31, October 1, 2023 Operating leases: Right-of-use assets $ 179,513 $ 175,932 Lease liabilities: Current 68,091 65,005 Non-current 139,537 144,685 Total operating lease liabilities $ 207,628 $ 209,690 Weighted-average remaining lease term: Operating leases 5 years 5 years Weighted-average discount rate: Operating leases 3.1 % 3.0 % At December 31, 2023, we had $8.5 million of operating leases that have not yet commenced. A maturity analysis of the future undiscounted cash flows associated with our lease liabilities at December 31, 2023 is as follows (in thousands): Operating 2024 (remaining) $ 57,581 2025 56,335 2026 38,422 2027 26,272 2028 17,751 Beyond 27,148 Total lease payments 223,509 Less: imputed interest (15,881) Total present value of lease liabilities $ 207,628

Stockholders' Equity and Stock

Stockholders' Equity and Stock Compensation Plans	3 Months Ended
Stockholders' Equity and Stock Compensation Plans	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Stockholders' Equity and Stock Compensation Plans	Stockholders’ Equity and Stock Compensation Plans We recogniz

Earnings per Share ("EPS")

Earnings per Share ("EPS")	3 Months Ended
Earnings per Share ("EPS")	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings per Share ("EPS")	Earnings per Share (“EPS”) Basic EPS is computed by dividing net income available to common stockholders by the weighted-average number of common shares outstanding, less unvested restricted stock for the period. Diluted EPS is computed by dividing net income by the weighted-average number of common shares outstanding and dilutive potential common shares for the period. Potential common shares include the weighted-average dilutive effects of outstanding stock options and unvested restricted stock using the treasury stock method. The following table presents the number of weighted-average shares used to compute basic and diluted EPS (in thousands, except per share data): Three Months Ended December 31, January 1, Net income attributable to Tetra Tech $ 74,972 $ 116,706 Weighted-average common shares outstanding – basic 53,317 53,069 Effect of dilutive stock options and unvested restricted stock 421 460 Weighted-average common shares outstanding – diluted 53,738 53,529 Earnings per share attributable to Tetra Tech: Basic $ 1.41 $ 2.20 Diluted $ 1.40 $ 2.18 For the first quarters of fiscal 2024 and 2023, no options were excluded from the calculation of dilutive potential common shares. The Convertible Notes described in Note 14 "Long-Term Debt", had no impact on the calculation of dilutive potential common shares in the first quarter of fiscal 2024, as the price of our common stock did not exceed the conversion price. The Capped Call Transactions were excluded from the calculation of dilutive potential common shares as their effect is anti-dilutive.

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rates for the first three months of fiscal 2024 and 2023 were 26.1% and 24.5%, respectively. Income tax expense was reduced by $1.0 million and $1.7 million of excess tax benefits on share-based payments in the first quarters of fiscal 2024 and 2023, respectively. Excluding the impact of the excess tax benefits on share-based payments, our effective tax rates in the first quarters of fiscal 2024 and 2023 were 27.1% and 25.7%, respectively. At December 31, 2023 and October 1, 2023, the liability for income taxes associated with uncertain tax positions was $61.7 million and $62.0 million, respectively. These liabilities represent our current estimates of the additional tax liabilities that we may be assessed when the related audits are concluded. If these audits are resolved in a manner more unfavorable than our current expectations, our additional tax liabilities could be materially higher than the amounts currently recorded resulting in additional tax expense.

Reportable Segments

Reportable Segments	3 Months Ended
Reportable Segments	Dec. 31, 2023
Segment Reporting [Abstract]
Reportable Segments	Reportable Segments We manage our operations under two reportable segments. Our GSG reportable segment primarily includes activities with U.S. government clients (federal, state and local) and all activities with development agencies worldwide. Our CIG reportable segment primarily includes activities with U.S. commercial clients and international clients other than development agencies. GSG provides high-end consulting and engineering services primarily to U.S. government clients (federal, state and local) and international development agencies worldwide. GSG supports U.S. government civilian and defense agencies with services in water, environment, sustainable infrastructure, information technology and disaster management. GSG also provides engineering design services for U.S. based federal and municipal clients, especially in water infrastructure, flood protection and solid waste. GSG also leads our support for development agencies worldwide, especially in the United States, United Kingdom and Australia. CIG primarily provides high-end consulting and engineering services to U.S. commercial clients, and international clients inclusive of the commercial and government sectors. CIG supports commercial clients worldwide in renewable energy, industrial, high performance buildings and aerospace markets. CIG also provides sustainable infrastructure and related environmental, engineering and project management services to commercial and local government clients across Canada, in Asia Pacific (primarily Australia and New Zealand), Europe, the United Kingdom and South America (primarily Brazil and Chile). Management evaluates th e performance of these reportable segments based upon their respective segment operating income before the effect of amortization expense related to acquisitions, and other unallocated corporate expenses. We account for inter-segment revenues and transfers as if they were to third parties; that is, by applying a negotiated fee onto the costs of the services performed. All significant intercompany balances and transactions are eliminated in consolidation. The following tables summarize financial information regarding our reportable segments (in thousands): Three Months Ended December 31, January 1, Revenue GSG $ 575,041 $ 471,067 CIG 669,107 439,556 Elimination of inter-segment revenue (15,881) (15,857) Total revenue $ 1,228,267 $ 894,766 Income from operations GSG $ 63,127 $ 60,347 CIG 71,401 50,108 Corporate (1) (23,447) (18,405) Total income from operations $ 111,081 $ 92,050 (1) Includes amortization of intangibles, acquisition and integration expenses, as well as other costs and other income not allocable to our reportable segments. Balance at December 31, October 1, Total Assets GSG $ 584,208 $ 543,066 CIG 1,065,638 994,470 Corporate (1) 2,300,977 2,282,941 Total assets $ 3,950,823 $ 3,820,477 (1) Corporate assets consist of intercompany eliminations and assets not allocated to our reportable segments including goo dwill, intangible assets, deferred income taxes and certain other assets

Fair Value Measurements

Fair Value Measurements	3 Months Ended
Fair Value Measurements	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We classified our assets and liabilities that were carried at fair value in one of the following categories: • Level 1: Quoted market prices in active markets for identical assets or liabilities. • Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data. • Level 3: Unobservable inputs that are not corroborated by market data. Derivative Instruments. Our derivative instruments are categorized within Level 2 of the fair value hierarchy. For additional information about our derivative financial instruments (see Note 15, "Derivative Financial Instruments"). Contingent Consideration. We measure our contingent earn-out liabilities at fair value on a recurring basis using significant unobservable inputs classified within Level 3 of the fair value hierarchy. (see Note 4, "Acquisitions" for further information). Debt. The fair value of long-term debt was determined using the present value of future cash flows based on the borrowing rates currently available for debt with similar terms and maturities (Level 2 measurement, as described in “Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K for the fiscal year ended October 1, 2023). The carrying value of our long-term debt under our Credit Facility approximated fair value at December 31, 2023 and October 1, 2023. At December 31, 2023, we had $385 million in outstanding borrowings under the Amended Credit Agreement, which was comprised of $320 million under the New Term Loan Facility and $65 million under the Amended Revolving Credit Facility. The estimated fair value of our $575 million Convertible Senior Notes (the "Convertible Notes") was determined based on the trading price of the Convertible Notes as of the last trading day of our first quarter of fiscal 2024. We consider the fair value of the Convertible Notes to be a Level 2 measurement as they are not actively traded in markets. The carrying amounts and estimated fair values of the Convertible notes were approximately $562 million and $603 million, respectively, at December 31, 2023, and $561 million and $566 million, respectively, at October 1, 2023. The Credit Facility and Convertible Notes were used to fund our business acquisitions, working capital needs, dividends, capital expenditures and contingent earn-outs.

Long-Term Debt

Long-Term Debt	3 Months Ended
Long-Term Debt	Dec. 31, 2023
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consisted of the following (in thousands): Balance at December 31, October 1, Credit facilities $ 385,000 $ 320,000 Convertible notes 575,000 575,000 Debt issuance costs and discount (14,681) (15,471) Long-term debt $ 945,319 $ 879,529 On August 22, 2023, we issued $575.0 million in convertible notes that bear interest at a rate of 2.25% per annum payable in arrears on February 15 and August 15 of each year, beginning on February 15, 2024 and mature on August 15, 2028, unless converted, redeemed or repurchased. Prior to May 15, 2028, the Convertible Notes will be convertible at the option of the holders only upon the occurrence of certain events and during certain periods. Thereafter, the Convertible Notes will be convertible at the option of the holders at any time until the close of business on the second scheduled trading day immediately preceding the maturity date. The initial conversion rate applicable to the Convertible Notes is 5.0855 shares of our common stock per $1,000 principal amount of the Convertible Notes, which is equivalent to an initial price of approximately $196.64 per share of our common stock, subject to adjustment if certain events occur. Upon conversion, we will pay cash up to the aggregate principal amount of the Convertible Notes to be converted and pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, in respect of the remainder, if any, of our conversion obligation in excess of the aggregate principal amount of the Convertible Notes being converted. In addition, upon the occurrence of a "fundamental change" as defined in the indenture governing the Convertible Notes, holders may require us to repurchase for cash all or any portion of their Convertible Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased plus any accrued and unpaid interest. If certain corporate events occur prior to the maturity date of the Convertible Notes or if we deliver a notice of redemption, we will, in certain circumstances, increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such event or notice of redemption. We will not be able to redeem the Convertible Notes prior to August 20, 2026. On or after August 20, 2026, we have the option to redeem for cash all or any portion of the Convertible Notes if the last reported sale price of our common stock is equal to or greater than 130% of the conversion price for a specified period of time at a redemption price equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus any accrued but unpaid interest. In addition, as described in the indenture governing the Convertible Notes, certain events of default including, but not limited to, bankruptcy, insolvency or reorganization, may result in the Convertible Notes becoming due and payable immediately. Our net proceeds from the offering were approximately $560.5 million after deducting the initial purchasers’ discounts and commissions and offering expenses. We used approximately $51.8 million of the net proceeds to pay the cost of the capped call transactions described below. We used the remaining net proceeds to repay all $185.0 million principal amount outstanding under our revolving credit facility, the remaining $234.4 million principal amount outstanding under our senior secured term loan due 2027 and approximately $89.4 million principal amount outstanding under our senior secured term loan due 2026. The Convertible Notes were recorded as a single unit within "Long-term debt" in our consolidated balance sheets as the conversion option within the Convertible Notes was not a derivative that would require bifurcation and the Convertible Notes did not involve a substantial premium. Transaction costs to issue the Convertible Notes were recorded as direct deductions from the related debt liabilities and amortized to interest expense using the effective interest method over the terms of the Convertible Notes. Debt issuance costs for the Convertible Notes have been amortized to interest expense over the terms of the Convertible Notes at an effective annual interest rate of 2.79%. The net carrying amount of the Convertible Notes was as follows (in thousands) : Balance at December 31, October 1, Principal $ 575,000 $ 575,000 Unamortized discount and issuance costs (13,481) (14,158) Net carrying amount $ 561,519 $ 560,842 The following table sets forth the interest expense recognized related to the Convertible Notes for the first quarter of fiscal 2024 (in thousands) : Amount Interest expense 3,270 Amortization of discount and issuance costs 678 Total interest expense $ 3,948 Concurrent with the offering of the Convertible Notes, in August 2023, we entered into capped call transactions (the "Capped Call Transactions"). The Capped Call Transactions are expected generally to reduce the potential dilution of our common stock upon conversion of the Convertible Notes and/or offset any cash payments we elect to make in excess of the principal amount of converted Convertible Notes, as the case may be. If, however, the market price per share of our common stock, as measured under the terms of the Capped Call Transactions, exceeds the cap price of the Capped Call Transactions, there would nevertheless be dilution and/or there would not be an offset of such cash payments, in each case, to the extent that such market price exceeds the cap price of the Capped Call Transactions. The cap price of the Capped Call Transactions is initially $259.56 per share, which represents a premium of 65% over the last reported sale price of our common stock of $157.31 per share on the NASDAQ Global Select Market on August 17, 2023, and is subject to certain adjustments under the terms of the Capped Call Transactions. We recorded the Capped Call Transactions as separate transactions from the issuance of the Convertible Notes. The cost of $51.8 million incurred to purchase the Capped Call Transactions was recorded as a reduction to additional paid-in capital (net of $12.9 million in deferred taxes) on our consolidated balance sheet as of fiscal 2023 year-end. On October 26, 2022, we entered into a Third Amended and Restated Credit Agreement that provides for an additional $500 million senior secured term loan facility (the "New Term Loan Facility") increasing our total borrowing capacity to $1.55 billion. On January 23, 2023, we drew the entire amount of the New Term Loan Facility to partially finance the RPS acquisition. The New Term Loan Facility is not subject to any amortization payments of principal and matures on the third anniversary of the RPS acquisition closing date in January 2026. On February 18, 2022, we entered into Amendment No. 2 to Second Amended and Restated Credit Agreement (“Amended Credit Agreement”) with a total borrowing capacity of $1.05 billion that will mature in February 2027. The Amended Credit Agreement is a $750 million senior secured, five-year facility that provides for a $250 million term loan facility (the “Amended Term Loan Facility”) and a $500 million revolving credit facility (the “Amended Revolving Credit Facility”). In addition, the Amended Credit Agreement includes a $300 million accordion feature that allows us to increase the Amended Credit Agreement to $1.05 billion subject to lender approval. The Amended Credit Agreement provides for, among other things, (i) refinance indebtedness under our Credit Agreement dated at July 30, 2018; (ii) finance open market repurchases of common stock, acquisitions, and cash dividends and distributions; and (iii) utilize the proceeds for working capital, capital expenditures and other general corporate purposes. The Amended Credit Agreement provides for a reduction in the interest grid for meeting certain sustainability targets related to the (i) reduction of greenhouse gas emissions through the Company’s projects and operational sustainability initiatives and (ii) improvement of peoples’ lives as a result of the Company’s projects that provide environmental, social and governance benefits. The Amended Revolving Credit Facility includes a $100 million sublimit for the issuance of standby letters of credit, a $20 million sublimit for swingline loans and a $300 million sublimit for multicurrency borrowings and letters of credit. The entire Amended Term Loan Facility was drawn on February 18, 2022. We may borrow on the Amended Revolving Credit Facility, at our option, at either (a) a benchmark rate plus a margin that ranges from 1.000% to 1.875% per annum, or (b) a base rate for loans in U.S. dollars (the highest of the U.S. federal funds rate plus 0.50% per annum, the bank’s prime rate or the Secured Overnight Financing Rate ("SOFR") rate plus 1.00%, plus a margin that ranges from 0% to 0.875% per annum. In each case, the applicable margin is based on our Consolidated Leverage Ratio, calculated quarterly. The Amended Term Loan Facility is subject to the same interest rate provisions. The Amended Credit Agreement expires on February 18, 2027, or earlier at our discretion upon payment in full of loans and other obligations. At December 31, 2023, we had $385 million in outstanding borrowings under the Amended Credit Agreement, which was comprised of $320 million under the New Term Loan Facility and $65 million under the Amended Revolving Credit Facility. For the first quarter of fiscal 2024, the weighted-average interest rate of the outstanding borrowings under the Amended Credit Agreement was 6.75%. In addition, we had $0.7 million in standby letters of credit under the Amended Credit Agreement. At December 31, 2023, we had $434.3 million of available credit under the Amended Revolving Credit Facility, all of which could be borrowed without a violation of our debt covenants. The Amended Credit Agreement contains certain affirmative and restrictive covenants, and customary events of default. The financial covenants provide for a maximum Consolidated Leverage Ratio of 3.25 to 1.00 (total funded debt/EBITDA, as defined in the Amended Credit Agreement) and a minimum Consolidated Interest Coverage Ratio of 3.00 to 1.00 (EBITDA/Consolidated Interest Charges, as defined in the Amended Credit Agreement). Our obligations under the Amended Credit Agreement are guaranteed by certain of our domestic subsidiaries and are secured by first priority liens on (i) the equity interests of certain of our subsidiaries, including those subsidiaries that are guarantors or borrowers under the Amended Credit Agreement, and (ii) the accounts receivable, general intangibles and intercompany loans and those of our subsidiaries that are guarantors or borrowers. At December 31, 2023, we were in compliance with these covenants with a consolidated leverage ratio of 1.84x and a consolidated interest coverage ratio of 9.49x.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
Derivative Financial Instruments	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments We use certain interest rate derivative contracts to hedge interest rate exposures on our variable rate debt. We also enter into foreign currency derivative contracts with financial institutions to reduce the risk that cash flows and earnings could adversely be affected by foreign currency exchange rate fluctuations. Our hedging program is not designated for trading or speculative purposes. We recognize derivative instruments as either assets or liabilities on the accompanying consolidated balance sheets at fair value. We record changes in the fair value (i.e., gains or losses) of the derivatives that have been designated as cash flow hedges in our consolidated balance sheets as accumulated other comprehensive income, and in our consolidated statements of income for those derivatives designated as fair value hedges. Our derivative contracts are categorized within Level 2 of the fair value hierarchy. In the fourth quarter of fiscal 2022, we entered into a forward contract to acquire GBP 714.0 million at a rate of 1.0852 for a total of USD 774.8 million that was integrated with our plan to acquire RPS. This contract matured on December 30, 2022. On December 28, 2022, we entered into an extension of the integrated forward contract to acquire GBP 714.0 million at a rate of 1.086 for a total of USD 775.4 million, extending the maturity date to January 23, 2023, the closing date of the RPS acquisition. Although an effective economic hedge of our foreign exchange risk related to this transaction, the forward contract did not qualify for hedge accounting. As a result, the forward contract was marked-to-market with changes in fair value recognized in earnings each period. The intrinsic value of the forward contract was immaterial at inception as the GBP/USD spot and forward exchange rates were essentially the same. The fair value of the forward contract at October 2, 2022 was $19.9 million, and an unrealized gain of the same amount was recognized in our fourth quarter of fiscal 2022 results. On January 23, 2023, the forward contract was settled at the fair value of $109.3 million. We recognized additional gains of $68.0 million and $21.4 million in the first and second quarters of fiscal 2023, respectively. All gains related to this transaction were reported in “Other non-operating income" on our consolidated income statements for the respective periods. In fiscal 2018, we entered into five interest rate swap agreements that we designated as cash flow hedges to fix the interest rate on the borrowings under our term loan facility. The five swaps expired on July 31, 2023. The related loss of $0.1 million was recognized and reported on our consolidated statement of comprehensive income for the first quarter of fiscal 2023. There were no derivative instruments that were not designated as hedging instruments for the first quarters of fiscal 2024 and 2023.

Reclassifications Out of Accumu

Reclassifications Out of Accumulated Other Comprehensive Income	3 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Reclassifications Out of Accumulated Other Comprehensive Income	Reclassifications Out of Accumulated Other Comprehensive Income The accumulated balances and activities for the three months ended December 31, 2023 and January 1, 2023 related to reclassifications out of accumulated other comprehensive income are summarized as follows (in thousands): Three Months Ended Foreign Gain (Loss) Net Pension Adjustments Accumulated Other Comprehensive Income (Loss) Balance at October 2, 2022 $ (210,556) $ 2,412 — $ (208,144) Other comprehensive income (loss) before reclassifications 33,107 (535) — 32,572 Amounts reclassified from accumulated other comprehensive loss: Interest rate contracts, net of tax (1) — 446 — 446 Net current-period other comprehensive income (loss) 33,107 (89) — 33,018 Balance at January 1, 2023 $ (177,449) $ 2,323 $ — $ (175,126) Balance at October 1, 2023 $ (197,933) $ — 2,638 $ (195,295) Other comprehensive income (loss) before reclassifications 63,106 — (13) 63,093 Net current-period other comprehensive income (loss) 63,106 — (13) 63,093 Balance at December 31, 2023 $ (134,827) $ — $ 2,625 $ (132,202) (1) This accumulated other comprehensive component is reclassified to “Interest expense” in our consolidated statements of income. See Note 15 “Derivative Financial Instruments”, for more information.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies We are subject to certain claims and lawsuits typically filed against the consulting and engineering profession, alleging primarily professional errors or omissions. We carry professional liability insurance, subject to certain deductibles and policy limits, against such claims. However, in some actions, parties are seeking damages that exceed our insurance coverage or for which we are not insured. While management does not believe that the resolution of these claims will have a material adverse effect, individually or in aggregate, on our financial position, results of operations or cash flows, management acknowledges the uncertainty surrounding the ultimate resolution of these matters. On July 15, 2019, following an initial January 14, 2019 filing, the Civil Division of the United States Attorney's Office filed an amended complaint in intervention in three qui tam actions filed against our subsidiary, Tetra Tech EC, Inc. ("TtEC"), in the U.S. District Court for the Northern District of California. The complaint alleges False Claims Act violations and breach of contract related to TtEC's contracts to perform environmental remediation services at the former Hunters Point Naval Shipyard in San Francisco, California. TtEC disputes the claims and will defend this matter vigorously. We are currently unable to determine the probability of the outcome of this matter or the range of reasonably possible loss, if any.

Related Party Transactions

Related Party Transactions	3 Months Ended
Related Party Transactions	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions We often provide services to unconsolidated joint ventures. Our revenue related t o services we provided to unconsolidated joint ventures for the first quarters of fiscal 2024 and 2023 was approxima tely $19 million and $23 million, respectively. Our related reimbursable costs for the first quarters of fiscal 2024 and 2023 were approximately $18 million a nd $22 million, respectively. Our consolidated balance sheets also included the following amounts related to these services (in thousands): Balance at December 31, October 1, 2023 Accounts receivable, net $ 23,501 $ 19,944 Contract assets 2,203 2,723 Contract liabilities 4,025 3,158

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Policies)	3 Months Ended
Recent Accounting Pronouncements (Policies)	Dec. 31, 2023
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	In November 2021, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2021-10, Government Assistance (Topic 832) , which requires annual disclosures for transactions with a government authority that are accounted for by applying a grant or contribution model by analogy, including (1) the types of transactions, (2) the accounting for those transactions, and (3) the effect of those transactions on an entity's financial statements. ASU 2021-10 was effective for us beginning in the first quarter of fiscal 2023. In fiscal 2020, the Canadian federal government implemented the Canadian Emergency Wage Subsidy ("CEWS") program in response to the negative impact of the coronavirus disease 2019 pandemic on businesses operating in Canada. Some of our Canadian legal entities qualified for and applied for these CEWS cash benefits to partially offset the impacts of revenue reductions and on-going staffing costs. The $21 million total received was initially recorded in "Other long-term liabilities" until all potential amendments to the qualification criteria, including some that were proposed with retroactive application, were finalized in fiscal 2022. In the first quarter of fiscal 2024, we distributed approximately $10 million to our Canadian employees. The remaining $11 million, which we expect to distribute within one year, is reported in "Accrued compensation". We do not expect there will be any related impact on our operating income, and we have no outstanding applications for further government assistance. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires that an entity report segment information in accordance with Topic 280, Segment Reporting. The amendments in the ASU are intended to improve reportable segment disclosure requirements primarily through enhanced disclosures about significant segment expenses. The amendments in this ASU are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024 (fiscal 2025 for us). Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which requires that an entity, on an annual basis, disclose additional income tax information, primarily related to the rate reconciliation and income taxes paid. The amendments in the ASU are intended to enhance the transparency and decision usefulness of income tax disclosures. The amendments in this ASU are effective for annual periods beginning after December 15, 2024 (fiscal 2026 for us). Early adoption is permitted. We are currently evaluating the impact of this guidance on our consolidated financial statements; however, we do not plan to adopt Topic 740 before fiscal 2026.
Revenue and Contract Assets and Contract Liabilities	We invoice customers based on the contractual terms of each contract. However, the timing of revenue recognition may differ from the timing of invoice issuance. Contract assets represent revenue recognized in excess of the amounts for which we have the contractual right to bill our customers. Such amounts are recoverable from customers based upon various measures of performance, including achievement of certain milestones or completion of a contract. In addition, many of our time and materials arrangements are billed in arrears pursuant to contract terms that are standard within the industry, resulting in contract assets and/or unbilled receivables being recorded, as revenue is recognized in advance of billings. Contract retentions, included in contract assets, represent amounts withheld by clients until certain conditions are met or the project is completed, which may extend beyond one year. Our RUPO represents a measure of the total dollar value of work to be performed on contracts awarded and in progress. We had $4.7 billion of RUPO at December 31, 2023. RUPO increases with awards from new contracts or additions on existing contracts, and decreases as work is performed and revenue is recognized on existing contracts. RUPO may also decrease when projects are canceled or modified in scope. We include a contract within our RUPO when the contract is awarded and an agreement on contract terms has been reached.
Accounts Receivable, Net	Billed accounts receivable represent amounts billed to clients that have not been collected. Unbilled accounts receivable, which represent an unconditional right to payment subject only to the passage of time, include unbilled amounts typically resulting from revenue recognized but not yet billed pursuant to contract terms or billed after the period end date. Substantially all of our unbilled receivables at December 31, 2023 are expected to be billed and collecte d within 12 months. The allowance for doubtful accounts represents amounts that are expected to become uncollectible or unrealizable in the future. We determine an estimated allowance for uncollectible accounts based on management's consideration of trends in the actual and forecasted credit quality of our clients, including delinquency and payment history; type of client, such as a government agency or a commerci al sector client; and general economic and industry conditions , which may affect our clients' ability to pay .
Fair Value Measurement, Policy	We classified our assets and liabilities that were carried at fair value in one of the following categories: • Level 1: Quoted market prices in active markets for identical assets or liabilities. • Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data. • Level 3: Unobservable inputs that are not corroborated by market data. Derivative Instruments. Our derivative instruments are categorized within Level 2 of the fair value hierarchy. For additional information about our derivative financial instruments (see Note 15, "Derivative Financial Instruments"). Contingent Consideration. We measure our contingent earn-out liabilities at fair value on a recurring basis using significant unobservable inputs classified within Level 3 of the fair value hierarchy. (see Note 4, "Acquisitions" for further information). Debt.

Revenue and Contract Balances (

Revenue and Contract Balances (Tables)	3 Months Ended
Revenue and Contract Balances (Tables)	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Summary of revenue disaggregated by client sector and contract type	The following tables present revenue disaggregated by client sector and contract type (in thousands): Three Months Ended December 31, January 1, Client Sector: U.S. federal government (1) $ 382,076 $ 276,075 U.S. state and local government 150,925 153,195 U.S. commercial 222,430 198,956 International (2) 472,836 266,540 Total $ 1,228,267 $ 894,766 Contract Type: Fixed-price $ 471,442 $ 327,737 Time-and-materials 549,651 420,570 Cost-plus 207,174 146,459 Total $ 1,228,267 $ 894,766 (1) Includes revenue generated under U.S. federal government contracts performed outside the United States. (2) Includes revenue generated from non-U.S. clien ts, primarily in Canada, Australia, Europe and the United Kingdom.
Summary of net contract assets/liabilities	Net contract assets/liabilities consisted of the following (in thousands): Balance at December 31, October 1, 2023 Contract assets (1) $ 89,073 $ 113,939 Contract liabilities 382,862 335,044 Net contract liabilities $ (293,789) $ (221,105) (1) Inclu
Components of net accounts receivable	Net accounts receivable consisted of the following (in thousands): Balance at December 31, October 1, Billed $ 700,880 $ 672,712 Unbilled 344,628 306,788 Total accounts receivable 1,045,508 979,500 Allowance for doubtful accounts (4,998) (4,965) Total accounts receivable, net $ 1,040,510 $ 974,535
Remaining performance obligation, expected timing	We expect to satisfy our RUPO at December 31, 2023 over the following periods (in thousands): Amount Within 12 months $ 3,149,015 Beyond 1,558,073 Total $ 4,707,088

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
Acquisitions (Tables)	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Schedule of recognized identified assets acquired and liabilities assumed	The table below represents the purchase price allocation for RPS based on estimates, assumptions, valuations and other analyses as of January 23, 2023. The purchase consideration, excluding the aforementioned forward contract gain, was allocated to the tangible and intangible assets, and liabilities of RPS based on their estimated fair values, with any excess purchase consideration allocated to goodwill as follows (in thousands): Amount Cash and cash equivalents $ 32,093 Accounts receivable and contract assets 202,303 Prepaid expenses and other current assets 45,999 Income taxes receivables 1,999 Property and equipment 38,435 Right-of-use assets, operating leases 40,179 Intangible assets 174,094 Deferred income taxes 35,084 Other long-term assets 1,061 Total assets acquired 571,247 Accounts payable $ (44,376) Accrued compensation (19,073) Contract liabilities (46,287) Income tax payable (7,083) Short-term lease liabilities, operating leases (13,477) Other current liabilities (135,474) Current portion of long-term debt (91,973) Long-term lease liabilities, operating leases (26,702) Other long-term liabilities (13,742) Deferred tax liabilities (41,613) Total liabilities assumed (439,800) Fair value of net assets acquired 131,447 Goodwill 652,762 Total purchase consideration $ 784,209
Schedule of acquired finite-lived intangible assets by major class	The following table summarizes the estimated fair values that were assigned to intangible assets at the acquisition date: Fair Value Weighted-Average Estimated Useful Life (in thousands) (in years) Backlog $ 27,880 1.6 Trade names 27,260 3.0 Client relations 118,954 11.1 Total intangible assets acquired $ 174,094 8.3
Business acquisition, pro forma information	Following are the supplemental consolidated financial results of Tetra Tech and RPS for the first quarter of fiscal 2023 on an unaudited pro forma basis, as if the RPS acquisition had been consummated as of the beginning of fiscal 2022 (in thousands): Three Months Ended January 1, Revenue $ 1,107,301 Net Income including noncontrolling interests $ 63,701
Schedule of estimated contingent earn out liabilities	The following table summarizes the changes in the fair value of estimated contingent consideration for the first quarters of fiscal 2024 and 2023 (in thousands): Three Months Ended December 31, January 1, Beginning balance $ 73,422 $ 65,566 Payments of contingent consideration (18,862) — Adjustments to fair value recorded in earnings (37) 933 Interest accretion expense 471 513 Effect of foreign currency exchange rate changes 610 2,017 Ending balance $ 55,604 $ 69,029 Maximum potential payout at end of period $ 92,253 $ 120,882

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
Goodwill and Intangible Assets (Tables)	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of changes in the carrying value of goodwill	The following table summarizes the changes in the carrying value of goodwill by reportable segment (in thousands): GSG CIG Total Balance at October 1, 2023 $ 659,942 $ 1,220,302 $ 1,880,244 Translation adjustments 2,731 40,171 42,902 Balance at December 31, 2023 $ 662,673 $ 1,260,473 $ 1,923,146
Summary of acquired identifiable intangible assets with finite useful lives	The following table presents the gross amount and accumulated amortization of our acquired identifiable intangible assets with finite useful lives included in “Intangible assets, net” on the consolidated balance sheets ($ in thousands): Period Ended December 31, 2023 October 1, 2023 Weighted- Gross Accumulated Net Amount Gross Accumulated Net Amount Client relations 9.2 $ 175,486 $ (41,572) $ 133,914 $ 169,217 $ (36,072) $ 133,145 Backlog 0.8 66,052 (54,960) 11,092 63,825 (47,802) 16,023 Trade names 2.1 39,084 (15,956) 23,128 37,411 (12,643) 24,768 Total $ 280,622 $ (112,488) $ 168,134 $ 270,453 $ (96,517) $ 173,936
Estimated amortization expense for the remainder of the fiscal year and the succeeding years	Estimated amortization expense for the remainder of fiscal 2024 and succeeding years is as follows (in thousands): Amount 2024 (remaining) $ 31,021 2025 29,138 2026 20,563 2027 14,440 2028 13,930 Beyond 59,042 Total $ 168,134

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
Property and Equipment (Tables)	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of components of property and equipment	Property and equipment consisted of the following (in thousands): Balance at December 31, October 1, Equipment, furniture and fixtures $ 136,873 $ 132,744 Leasehold improvements 40,942 44,733 Total property and equipment 177,815 177,477 Accumulated depreciation (102,844) (102,645) Property and equipment, net $ 74,971 $ 74,832

Stock Repurchase and Dividends

Stock Repurchase and Dividends (Tables)	3 Months Ended
Stock Repurchase and Dividends (Tables)	Dec. 31, 2023
Stock Repurchase And Dividends [Abstract]
Summary of dividends declared and paid	The following table presents dividends declared and paid in the first quarters of fis cal 2024 and 2023: Declare Date Dividend Paid Per Share Record Date Payment Date Dividend Paid November 13, 2023 $ 0.26 November 30, 2023 December 13, 2023 $ 13,873 November 7, 2022 $ 0.23 November 21, 2022 December 9, 2022 $ 12,186

Leases (Tables)

Leases (Tables)	3 Months Ended
Leases (Tables)	Dec. 31, 2023
Leases [Abstract]
Summary of components of lease cost	The components of lease costs are as follows (in thousands): Three Months Ended December 31, January 1, Operating lease cost $ 24,232 $ 20,961 Sublease (income) cost (57) (32) Total lease cost $ 24,175 $ 20,929 Supplemental cash flow information related to leases is as follows (in thousands): Three Months Ended December 31, January 1, Operating cash flows for operating leases $ 19,682 $ 16,493 Right-of-use assets obtained in exchange for new operating lease liabilities 9,803 11,117
Summary of supplemental balance sheet and other information	Supplemental balance sheet and other information related to leases are as follows (in thousands): Balance at December 31, October 1, 2023 Operating leases: Right-of-use assets $ 179,513 $ 175,932 Lease liabilities: Current 68,091 65,005 Non-current 139,537 144,685 Total operating lease liabilities $ 207,628 $ 209,690 Weighted-average remaining lease term: Operating leases 5 years 5 years Weighted-average discount rate: Operating leases 3.1 % 3.0 %
Summary of maturity of future undiscounted cash flows associated with operating lease liabilities	A maturity analysis of the future undiscounted cash flows associated with our lease liabilities at December 31, 2023 is as follows (in thousands): Operating 2024 (remaining) $ 57,581 2025 56,335 2026 38,422 2027 26,272 2028 17,751 Beyond 27,148 Total lease payments 223,509 Less: imputed interest (15,881) Total present value of lease liabilities $ 207,628

Earnings per Share ("EPS") (Tab

Earnings per Share ("EPS") (Tables)	3 Months Ended
Earnings per Share ("EPS") (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of number of weighted-average shares used to compute basic and diluted EPS	The following table presents the number of weighted-average shares used to compute basic and diluted EPS (in thousands, except per share data): Three Months Ended December 31, January 1, Net income attributable to Tetra Tech $ 74,972 $ 116,706 Weighted-average common shares outstanding – basic 53,317 53,069 Effect of dilutive stock options and unvested restricted stock 421 460 Weighted-average common shares outstanding – diluted 53,738 53,529 Earnings per share attributable to Tetra Tech: Basic $ 1.41 $ 2.20 Diluted $ 1.40 $ 2.18

Reportable Segments (Tables)

Reportable Segments (Tables)	3 Months Ended
Reportable Segments (Tables)	Dec. 31, 2023
Segment Reporting [Abstract]
Summarized financial information of reportable segments	The following tables summarize financial information regarding our reportable segments (in thousands): Three Months Ended December 31, January 1, Revenue GSG $ 575,041 $ 471,067 CIG 669,107 439,556 Elimination of inter-segment revenue (15,881) (15,857) Total revenue $ 1,228,267 $ 894,766 Income from operations GSG $ 63,127 $ 60,347 CIG 71,401 50,108 Corporate (1) (23,447) (18,405) Total income from operations $ 111,081 $ 92,050 (1) Includes amortization of intangibles, acquisition and integration expenses, as well as other costs and other income not allocable to our reportable segments. Balance at December 31, October 1, Total Assets GSG $ 584,208 $ 543,066 CIG 1,065,638 994,470 Corporate (1) 2,300,977 2,282,941 Total assets $ 3,950,823 $ 3,820,477 (1) Corporate assets consist of intercompany eliminations and assets not allocated to our reportable segments including goo dwill, intangible assets, deferred income taxes and certain other assets

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of long-term debt instruments	Long-term debt consisted of the following (in thousands): Balance at December 31, October 1, Credit facilities $ 385,000 $ 320,000 Convertible notes 575,000 575,000 Debt issuance costs and discount (14,681) (15,471) Long-term debt $ 945,319 $ 879,529
Convertible debt	The net carrying amount of the Convertible Notes was as follows (in thousands) : Balance at December 31, October 1, Principal $ 575,000 $ 575,000 Unamortized discount and issuance costs (13,481) (14,158) Net carrying amount $ 561,519 $ 560,842
Interest income and interest expense disclosure	The following table sets forth the interest expense recognized related to the Convertible Notes for the first quarter of fiscal 2024 (in thousands) : Amount Interest expense 3,270 Amortization of discount and issuance costs 678 Total interest expense $ 3,948

Reclassifications Out of Accu_2

Reclassifications Out of Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Summary of reclassifications out of accumulated other comprehensive income	The accumulated balances and activities for the three months ended December 31, 2023 and January 1, 2023 related to reclassifications out of accumulated other comprehensive income are summarized as follows (in thousands): Three Months Ended Foreign Gain (Loss) Net Pension Adjustments Accumulated Other Comprehensive Income (Loss) Balance at October 2, 2022 $ (210,556) $ 2,412 — $ (208,144) Other comprehensive income (loss) before reclassifications 33,107 (535) — 32,572 Amounts reclassified from accumulated other comprehensive loss: Interest rate contracts, net of tax (1) — 446 — 446 Net current-period other comprehensive income (loss) 33,107 (89) — 33,018 Balance at January 1, 2023 $ (177,449) $ 2,323 $ — $ (175,126) Balance at October 1, 2023 $ (197,933) $ — 2,638 $ (195,295) Other comprehensive income (loss) before reclassifications 63,106 — (13) 63,093 Net current-period other comprehensive income (loss) 63,106 — (13) 63,093 Balance at December 31, 2023 $ (134,827) $ — $ 2,625 $ (132,202) (1) This accumulated other comprehensive component is reclassified to “Interest expense” in our consolidated statements of income. See Note 15 “Derivative Financial Instruments”, for more information.

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
Related Party Transactions (Tables)	Dec. 31, 2023
Related Party Transactions [Abstract]
Schedule of related party transactions	Our consolidated balance sheets also included the following amounts related to these services (in thousands): Balance at December 31, October 1, 2023 Accounts receivable, net $ 23,501 $ 19,944 Contract assets 2,203 2,723 Contract liabilities 4,025 3,158

Recent Accounting Pronounceme_3

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Oct. 01, 2023
Accounting Changes and Error Corrections [Abstract]
Government assistance noncurrent liability		$ 21
Government assistance current liability	$ 11
Government assistance decrease in liability	$ 10

Revenue and Contract Balances -

Revenue and Contract Balances - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 1,228,267	$ 894,766
Fixed-price
Disaggregation of Revenue [Line Items]
Revenue	471,442	327,737
Time-and-materials
Disaggregation of Revenue [Line Items]
Revenue	549,651	420,570
Cost-plus
Disaggregation of Revenue [Line Items]
Revenue	207,174	146,459
U.S. federal government
Disaggregation of Revenue [Line Items]
Revenue	382,076	276,075
U.S. state and local government
Disaggregation of Revenue [Line Items]
Revenue	150,925	153,195
U.S. commercial
Disaggregation of Revenue [Line Items]
Revenue	222,430	198,956
International
Disaggregation of Revenue [Line Items]
Revenue	$ 472,836	$ 266,540

Revenue and Contract Balances_2

Revenue and Contract Balances - Summary of Contract Liabilities/Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Disaggregation of Revenue [Line Items]
Contract assets	$ 89,073	$ 113,939
Contract liabilities	382,862	335,044
Net contract liabilities	(293,789)	(221,105)
Contract Retentions
Disaggregation of Revenue [Line Items]
Contract assets	$ 6,000	$ 6,800

Revenue and Contract Balances_3

Revenue and Contract Balances - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Revenue from Contract with Customer [Abstract]
Contract liability revenue recognized during the period	$ 130,000	$ 81,000
Net favorable (unfavorable) revenue and operating income adjustments	5,700	$ 3,500
Liabilities for anticipated losses	9,200		$ 8,500
Estimated cost to complete the related contracts	$ 68,000		$ 68,000
Period for billing and collecting unbilled receivables	12 months
Remaining unsatisfied performance obligation	$ 4,707,088
Remaining performance obligation, termination notice period one	30 days
Remaining performance obligation, termination notice period two	60 days
Remaining performance obligation, termination notice period three	90 days

Revenue and Contract Balances_4

Revenue and Contract Balances - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Revenue from Contract with Customer [Abstract]
Billed	$ 700,880	$ 672,712
Unbilled	344,628	306,788
Total accounts receivable	1,045,508	979,500
Allowance for doubtful accounts	(4,998)	(4,965)
Total accounts receivable, net	$ 1,040,510	$ 974,535

Revenue and Contract Balances_5

Revenue and Contract Balances - Remaining Unsatisfied Performance Obligations (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining unsatisfied performance obligation	$ 4,707,088
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining unsatisfied performance obligation	$ 3,149,015
Remaining unsatisfied performance obligation, expected timing of satisfaction	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining unsatisfied performance obligation	$ 1,558,073
Remaining unsatisfied performance obligation, expected timing of satisfaction

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) £ / shares in Units, $ in Thousands, £ in Millions			3 Months Ended		12 Months Ended
	Jan. 23, 2023 USD ($) employee	Jan. 23, 2023 GBP (£) employee	Dec. 31, 2023 USD ($)	Jan. 01, 2023 USD ($)	Oct. 01, 2023 USD ($) employee program	Oct. 02, 2022 USD ($)	Sep. 23, 2022 £ / shares
Business Acquisition [Line Items]
Pence per share expected to be acquired \| £ / shares							£ 2.22
Acquisition and integration expenses			$ 0	$ 3,761
Minimum
Business Acquisition [Line Items]
Significant unobservable input, earn-out period			3 years
Minimum \| Existing customer contracts
Business Acquisition [Line Items]
Useful life of intangible assets			1 year
Maximum
Business Acquisition [Line Items]
Significant unobservable input, earn-out period			5 years
Maximum \| Existing customer contracts
Business Acquisition [Line Items]
Useful life of intangible assets			12 years
RPS Group PLC
Business Acquisition [Line Items]
Number of employees \| employee	5,000	5,000
Total purchase price	$ 784,000	£ 633
Acquisition and integration expenses					$ 33,200
Net purchase price	675,000
RPS Group PLC \| Foreign Exchange Forward
Business Acquisition [Line Items]
Foreign currency forward contract, asset fair value	$ 109,300					$ 19,900
Amyx, Inc.
Business Acquisition [Line Items]
Number of employees \| employee					500
Total purchase price					$ 120,900
Number of government programs acquired \| program					30
Payables related to promissory note					$ 100,000
Receivables (payables) related to estimated post-closing adjustments					8,700
Contingent earn-out liability					12,200
Aggregate maximum of contingent consideration					$ 25,000
All acquisitions
Business Acquisition [Line Items]
Aggregate maximum of contingent consideration			$ 92,253	$ 120,882

Acquisitions - Schedule of Purc

Acquisitions - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023	Jan. 23, 2023
Business Acquisition [Line Items]
Goodwill	$ 1,923,146	$ 1,880,244
RPS Group PLC
Business Acquisition [Line Items]
Cash and cash equivalents			$ 32,093
Accounts receivable and contract assets			202,303
Prepaid expenses and other current assets			45,999
Income taxes receivables			1,999
Property and equipment			38,435
Right-of-use assets, operating leases			40,179
Intangible assets			174,094
Deferred income taxes			35,084
Other long-term assets			1,061
Total assets acquired			571,247
Accounts payable			(44,376)
Accrued compensation			(19,073)
Contract liabilities			(46,287)
Income tax payable			(7,083)
Short-term lease liabilities, operating leases			(13,477)
Other current liabilities			(135,474)
Current portion of long-term debt			(91,973)
Long-term lease liabilities, operating leases			(26,702)
Other long-term liabilities			(13,742)
Deferred tax liabilities			(41,613)
Total liabilities assumed			(439,800)
Fair value of net assets acquired			131,447
Goodwill			652,762
Total purchase consideration			$ 784,209

Acquisitions - Schedule of Inta

Acquisitions - Schedule of Intangible Assets Assumed (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 23, 2023	Dec. 31, 2023
Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average Amortization Period (in years)		9 months 18 days
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average Amortization Period (in years)		2 years 1 month 6 days
Client relations
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average Amortization Period (in years)		9 years 2 months 12 days
RPS Group PLC
Acquired Finite-Lived Intangible Assets [Line Items]
Fair Value	$ 174,094
Weighted-average Amortization Period (in years)	8 years 3 months 18 days
RPS Group PLC \| Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Fair Value	$ 27,880
Weighted-average Amortization Period (in years)	1 year 7 months 6 days
RPS Group PLC \| Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Fair Value	$ 27,260
Weighted-average Amortization Period (in years)	3 years
RPS Group PLC \| Client relations
Acquired Finite-Lived Intangible Assets [Line Items]
Fair Value	$ 118,954
Weighted-average Amortization Period (in years)	11 years 1 month 6 days

Acquisitions - Supplemental Pro

Acquisitions - Supplemental Pro Forma Information (Details) - RPS Group PLC $ in Thousands	3 Months Ended
	Jan. 01, 2023 USD ($)
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 1,107,301
Net Income including noncontrolling interests	$ 63,701

Acquisitions - Schedule of Esti

Acquisitions - Schedule of Estimated Contingent Consideration (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
All acquisitions
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Aggregate maximum of contingent consideration	$ 92,253	$ 120,882
Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	73,422	65,566
Payments of contingent consideration	(18,862)	0
Adjustments to fair value recorded in earnings	(37)	933
Interest accretion expense	471	513
Effect of foreign currency exchange rate changes	610	2,017
Ending balance	$ 55,604	$ 69,029

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($)
Goodwill
Balance at beginning of the period	$ 1,880,244
Translation adjustments	42,902
Balance at end of the period	1,923,146
GSG
Goodwill
Balance at beginning of the period	659,942
Translation adjustments	2,731
Balance at end of the period	662,673
CIG
Goodwill
Balance at beginning of the period	1,220,302
Translation adjustments	40,171
Balance at end of the period	$ 1,260,473

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Narrative (Details) - USD ($)		3 Months Ended
	Jul. 03, 2023	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Goodwill [Line Items]
Impairment of goodwill	$ 0
Percentage of excess of fair value over carrying value (less than)	45%
Amortization expense		$ 12,500,000	$ 3,400,000
GSG
Goodwill [Line Items]
Gross amounts of goodwill		680,400,000		$ 677,600,000
Accumulated impairment		17,700,000		17,700,000
CIG
Goodwill [Line Items]
Gross amounts of goodwill		1,381,900,000		1,341,800,000
Accumulated impairment		$ 121,500,000		$ 121,500,000

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Gross Amount and Accumulated Amortization of Acquired Finite-lived Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Oct. 01, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 280,622	$ 270,453
Accumulated Amortization	(112,488)	(96,517)
Net Amount	$ 168,134	173,936
Client relations
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	9 years 2 months 12 days
Gross Amount	$ 175,486	169,217
Accumulated Amortization	(41,572)	(36,072)
Net Amount	$ 133,914	133,145
Backlog
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	9 months 18 days
Gross Amount	$ 66,052	63,825
Accumulated Amortization	(54,960)	(47,802)
Net Amount	$ 11,092	16,023
Trade names
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in Years)	2 years 1 month 6 days
Gross Amount	$ 39,084	37,411
Accumulated Amortization	(15,956)	(12,643)
Net Amount	$ 23,128	$ 24,768

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Estimated Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
2024 (remaining)	$ 31,021
2025	29,138
2026	20,563
2027	14,440
2028	13,930
Beyond	59,042
Net Amount	$ 168,134	$ 173,936

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 177,815		$ 177,477
Accumulated depreciation	(102,844)		(102,645)
Property and equipment, net	74,971		74,832
Depreciation expense related to property and equipment	7,000	$ 3,200
Equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	136,873		132,744
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 40,942		$ 44,733

Stock Repurchase and Dividend_2

Stock Repurchase and Dividends - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended
	Feb. 27, 2024	Jan. 29, 2024	Dec. 13, 2023	Dec. 09, 2022	Dec. 31, 2023	Jan. 01, 2023	Oct. 05, 2021
Subsequent Event [Line Items]
Remaining authorized amount under share repurchase program					$ 347.8
Dividend paid per share (in dollars per share)			$ 0.26	$ 0.23	$ 0.26	$ 0.23
Subsequent Event
Subsequent Event [Line Items]
Quarterly cash dividend declared (in dollars per share)		$ 0.26
Forecast
Subsequent Event [Line Items]
Dividend paid per share (in dollars per share)	$ 0.26
October 2021 Stock Repurchase Program
Subsequent Event [Line Items]
Maximum repurchase amount under stock repurchase program							$ 400

Stock Repurchase and Dividend_3

Stock Repurchase and Dividends - Schedule of Dividends Declared and Paid (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Dec. 13, 2023	Dec. 09, 2022	Dec. 31, 2023	Jan. 01, 2023
Stock Repurchase And Dividends [Abstract]
Dividend paid per share (in dollars per share)	$ 0.26	$ 0.23	$ 0.26	$ 0.23
Dividend Paid	$ 13,873	$ 12,186

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	Dec. 31, 2023 USD ($)
Lessee, Lease, Description [Line Items]
Renewal term (up to)	5 years
Operating leases, not yet commenced	$ 8.5
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	1 month
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	10 years

Leases - Components of Lease Co

Leases - Components of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Leases [Abstract]
Operating lease cost	$ 24,232	$ 20,961
Sublease (income) cost	(57)	(32)
Total lease cost	$ 24,175	$ 20,929

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Leases [Abstract]
Operating cash flows for operating leases	$ 19,682	$ 16,493
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 9,803	$ 11,117

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet and Other Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Operating leases:
Right-of-use assets	$ 179,513	$ 175,932
Lease liabilities:
Current	68,091	65,005
Non-current	139,537	144,685
Total operating lease liabilities	$ 207,628	$ 209,690
Weighted-average remaining lease term:
Operating leases	5 years	5 years
Weighted-average discount rate:
Operating leases	3.10%	3%

Leases - Maturity Analysis of t

Leases - Maturity Analysis of the Future Undiscounted Cash Flows of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Operating Leases
2024 (remaining)	$ 57,581
2025	56,335
2026	38,422
2027	26,272
2028	17,751
Beyond	27,148
Total lease payments	223,509
Less: imputed interest	(15,881)
Total present value of lease liabilities	$ 207,628	$ 209,690

Stockholders' Equity and Stoc_2

Stockholders' Equity and Stock Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7.6	$ 7.2
PSU's
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	55,836
Fair value of awards granted (in dollars per share)	$ 205.39
Vesting period	3 years
Percentage of shares that ultimately vest depending on growth in diluted earnings per share	50%
Percentage of shares that ultimately vest depending on the shareholder return relative to peer group of companies over vesting period	50%
RSU's
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	107,860
Fair value of awards granted (in dollars per share)	$ 164.27
RSU's \| Executive officers and employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
RSU's \| Non-employee director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year

Earnings per Share ("EPS") (Det

Earnings per Share ("EPS") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Earnings Per Share [Abstract]
Net income attributable to Tetra Tech, basic	$ 74,972	$ 116,706
Net income attributable to Tetra Tech, diluted	$ 74,972	$ 116,706
Weighted-average common shares outstanding – basic (in shares)	53,317	53,069
Effect of dilutive stock options and unvested restricted stock (in shares)	421	460
Weighted-average common stock outstanding – diluted (in shares)	53,738	53,529
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 1.41	$ 2.20
Diluted (in dollars per share)	$ 1.40	$ 2.18

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Income Tax Disclosure [Abstract]
Effective tax rate	26.10%	24.50%
Reduction in income tax expense due to excess tax benefits on share-based payments	$ 1	$ 1.7
Effective tax rate, excluding excess tax benefits on share-based payments	27.10%	25.70%
Liability for uncertain tax positions	$ 61.7		$ 62

Reportable Segments - Narrative

Reportable Segments - Narrative (Details)	3 Months Ended
Reportable Segments - Narrative (Details)	Dec. 31, 2023 segment
Segment Reporting [Abstract]
Number of reportable segments	2

Reportable Segments - Summary o

Reportable Segments - Summary of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Segment Reporting Information [Line Items]
Revenue	$ 1,228,267	$ 894,766
Income from operations	111,081	92,050
Total Assets	3,950,823		$ 3,820,477
Operating segments \| GSG
Segment Reporting Information [Line Items]
Revenue	575,041	471,067
Income from operations	63,127	60,347
Total Assets	584,208		543,066
Operating segments \| CIG
Segment Reporting Information [Line Items]
Revenue	669,107	439,556
Income from operations	71,401	50,108
Total Assets	1,065,638		994,470
Elimination of inter-segment revenue
Segment Reporting Information [Line Items]
Revenue	(15,881)	(15,857)
Corporate
Segment Reporting Information [Line Items]
Income from operations	(23,447)	$ (18,405)
Total Assets	$ 2,300,977		$ 2,282,941

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Debt Instrument [Line Items]
Convertible notes	$ 945,319	$ 879,529
Amended Credit Agreement
Debt Instrument [Line Items]
Amount outstanding under credit facility	385,000
Amended Credit Agreement \| New Term Loan Facility
Debt Instrument [Line Items]
Amount outstanding under credit facility	320,000
Amended Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Amount outstanding under credit facility	65,000
2028 Senior Notes \| Convertible Debt
Debt Instrument [Line Items]
Convertible notes	561,519	560,842
Convertible debt, estimated fair value	$ 603,000	$ 566,000

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Debt Instrument [Line Items]
Debt issuance costs and discount	$ (14,681)	$ (15,471)
Convertible notes	945,319	879,529
Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	385,000	320,000
Convertible Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 575,000	$ 575,000

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details)			3 Months Ended
Long-Term Debt - Narrative (Details)	Aug. 22, 2023 USD ($) $ / shares	Feb. 18, 2022 USD ($)	Dec. 31, 2023 USD ($)	Oct. 01, 2023 USD ($)	Aug. 17, 2023 $ / shares	Oct. 26, 2022 USD ($)
Line of Credit Facility [Line Items]
Derivative, cap price per share (in dollars per share) \| $ / shares	$ 259.56
Premium over reported sales price, percentage	0.65
Common stock, reported sales price (in dollars per share) \| $ / shares					$ 157.31
Deferred tax liabilities			$ 11,620,000	$ 14,256,000
Bank overdrafts			0
Convertible Debt
Line of Credit Facility [Line Items]
Payments for capped calls	$ 51,800,000
Deferred tax liabilities			12,900,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Repayments of long-term lines of credit	185,000,000
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount			57,400,000
Amended Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 750,000,000
Accordion feature, higher borrowing capacity option		$ 1,050,000,000				$ 1,550,000,000
Debt instrument term		5 years
Accordion feature, increase limit		$ 300,000,000
Amount outstanding under credit facility			$ 385,000,000
Weighted average interest rate, at point in time			6.75%
Debt covenant, maximum consolidated leverage ratio		3.25
Debt covenant, maximum consolidated leverage ratio		3
Ratio of indebtedness to net capital			1.84
Ratio of consolidated fixed charge coverage ratio			9.49
Amended Credit Agreement \| New Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 500,000,000
Amount outstanding under credit facility			$ 320,000,000
Amended Credit Agreement \| Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 250,000,000
Amended Credit Agreement \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 500,000,000
Amount outstanding under credit facility			65,000,000
Remaining borrowing capacity			434,300,000
Amended Credit Agreement \| Revolving Credit Facility \| Base Rate \| Secured Overnight Financing Rate (SOFR)
Line of Credit Facility [Line Items]
Basis spread on variable rate		1%
Amended Credit Agreement \| Revolving Credit Facility \| Base Rate \| Fed Funds Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.50%
Amended Credit Agreement \| Revolving Credit Facility \| Minimum \| Secured Overnight Financing Rate (SOFR)
Line of Credit Facility [Line Items]
Basis spread on variable rate		1%
Amended Credit Agreement \| Revolving Credit Facility \| Minimum \| Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		0%
Amended Credit Agreement \| Revolving Credit Facility \| Maximum \| Secured Overnight Financing Rate (SOFR)
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.875%
Amended Credit Agreement \| Revolving Credit Facility \| Maximum \| Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.875%
Amended Credit Agreement \| Standby Letters of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 100,000,000
Letters of credit outstanding, amount			$ 700,000
Amended Credit Agreement \| Swingline Loan
Line of Credit Facility [Line Items]
Maximum borrowing capacity		20,000,000
Amended Credit Agreement \| Multicurrency Borrowings and Letters of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 300,000,000
2028 Senior Notes \| Convertible Debt
Line of Credit Facility [Line Items]
Principal amount	$ 575,000,000
Stated interest percentage	2.25%
Conversion ratio	0.0050855
Conversion price (in dollars per share) \| $ / shares	$ 196.64
Redemption price, percentage			100%
Threshold percentage of stock price trigger			130%
Proceeds from convertible debt	$ 560,500,000
Interest rate, effective percentage			2.79%
Term Loan Facility Due 2027
Line of Credit Facility [Line Items]
Repayments of secured debt	234,400,000
Term Loan Facility Due 2026
Line of Credit Facility [Line Items]
Repayments of secured debt	$ 89,400,000
Other Credit Facilities
Line of Credit Facility [Line Items]
Amount outstanding under credit facility			$ 0

Long-Term Debt - Net Carrying A

Long-Term Debt - Net Carrying Amount of Senior Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 01, 2023
Debt Instrument [Line Items]
Debt issuance costs and discount	$ (14,681)	$ (15,471)
Long-term debt	945,319	879,529
Convertible Debt
Debt Instrument [Line Items]
Long-term debt, gross	575,000	575,000
2028 Senior Notes \| Convertible Debt
Debt Instrument [Line Items]
Long-term debt, gross	575,000	575,000
Debt issuance costs and discount	(13,481)	(14,158)
Long-term debt	$ 561,519	$ 560,842

Long-Term Debt - Schedule of In

Long-Term Debt - Schedule of Interest Expense (Details) - 2028 Senior Notes - Convertible Debt $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Interest expense	$ 3,270
Amortization of discount and issuance costs	678
Total interest expense	$ 3,948

Derivative Financial Instrume_2

Derivative Financial Instruments (Details) $ in Thousands, £ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2023 USD ($)	Apr. 02, 2023 USD ($)	Jan. 01, 2023 USD ($)	Sep. 30, 2018 agreement	Jan. 23, 2023 USD ($)	Dec. 28, 2022 USD ($)	Dec. 28, 2022 GBP (£)	Oct. 02, 2022 USD ($)	Oct. 02, 2022 GBP (£)
Derivative [Line Items]
Gain on foreign currency forward contract	$ 0		$ 67,995
Gains (losses) on cash flow hedges recognized in comprehensive income	$ 0		(89)
RPS Group PLC
Derivative [Line Items]
Derivative, forward exchange rate						1.086	1.086	1.0852	1.0852
Foreign Exchange Forward \| RPS Group PLC
Derivative [Line Items]
Notional amount						$ 775,400	£ 714	$ 774,800	£ 714
Foreign currency forward contract, asset fair value					$ 109,300			$ 19,900
Gain on foreign currency forward contract		$ 21,400	$ 68,000
Interest Rate Swap \| Designated as cash flow hedges \| Derivatives designated as hedging instruments
Derivative [Line Items]
Number of derivative agreements \| agreement				5

Reclassifications Out of Accu_3

Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023
Reclassifications out of accumulated other comprehensive income (loss)
Beginning balance	$ 1,403,506	$ 1,183,137
Amounts reclassified from accumulated other comprehensive loss:
Other comprehensive income, net of tax	63,093	33,018
Ending balance	1,537,687	1,323,967
Accumulated Other Comprehensive Income (Loss)
Reclassifications out of accumulated other comprehensive income (loss)
Beginning balance	(195,295)	(208,144)
Other comprehensive income (loss) before reclassifications	63,093	32,572
Amounts reclassified from accumulated other comprehensive loss:
Interest rate contracts, net of tax		446
Other comprehensive income, net of tax	63,093	33,018
Ending balance	(132,202)	(175,126)
Foreign Currency Translation Adjustments
Reclassifications out of accumulated other comprehensive income (loss)
Beginning balance	(197,933)	(210,556)
Other comprehensive income (loss) before reclassifications	63,106	33,107
Amounts reclassified from accumulated other comprehensive loss:
Interest rate contracts, net of tax		0
Other comprehensive income, net of tax	63,106	33,107
Ending balance	(134,827)	(177,449)
Gain (Loss) on Derivative Instruments
Reclassifications out of accumulated other comprehensive income (loss)
Beginning balance	0	2,412
Other comprehensive income (loss) before reclassifications	0	(535)
Amounts reclassified from accumulated other comprehensive loss:
Interest rate contracts, net of tax		446
Other comprehensive income, net of tax	0	(89)
Ending balance	0	2,323
Net Pension Adjustments
Reclassifications out of accumulated other comprehensive income (loss)
Beginning balance	2,638	0
Other comprehensive income (loss) before reclassifications	(13)	0
Amounts reclassified from accumulated other comprehensive loss:
Interest rate contracts, net of tax		0
Other comprehensive income, net of tax	(13)	0
Ending balance	$ 2,625	$ 0

Commitments and Contingencies (

Commitments and Contingencies (Details)	Jul. 15, 2019 action
Commitments and Contingencies Disclosure [Abstract]
Number of qui tam actions	3

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Jan. 01, 2023	Oct. 01, 2023
Related Party Transaction [Line Items]
Revenue	$ 1,228,267	$ 894,766
Reimbursable costs	18,000	22,000
Accounts receivable, net	1,040,510		$ 974,535
Contract assets	89,073		113,939
Contract liabilities	382,862		335,044
Related Party
Related Party Transaction [Line Items]
Revenue	19,000	$ 23,000
Accounts receivable, net	23,501		19,944
Contract assets	2,203		2,723
Contract liabilities	$ 4,025		$ 3,158