John Hancock GA Senior Loan Trust N-CSRCertified annual shareholder report (management investment company)

John Hancock GA Senior Loan Trust

Management's discussion of fund performance

MANAGED BY

Michael A. Foreman, Long Hoang, Daniel A. Walker, Henry Wong, and Ying Yi

Middle market LBO activity for sponsor-backed firms declined approximately 40% in 2023 from prior year due to macro uncertainties including volatility in the banking sector earlier in the year, high interest rate environment, cooling but still high inflation and geopolitical concerns. The dearth of deals promoted competition amongst direct lenders and drove spreads lower, declining 75-100bps from peak levels. While yields modestly declined, the direct lending asset class continued to benefit from elevated interest rates.

An improving economic backdrop towards the latter part of Q3 resulted in a pick-up in general M&A activity and the revival of the broadly syndicated loan market, which was sluggish in the first half of 2023. Refinancing and repricing transactions surged in the leveraged loan market driven by the positive outlook on interest rates. The private equity and private debt markets remain optimistic that M&A activity will continue to improve due to multiple rate cut expectations, mounting pressure on private equity GP's to deliver distribution to LP's and the pent-up demand for M&A both from sponsors, who are estimated to have over $1.3 Trillion of uncommitted capital raised, and direct lenders, estimated to have over $400 Billion in uncommitted capital raised.

John Hancock Senior Loan Trust returned 11.18% for the year ended December 31, 2023. The fund's benchmark, the Morningstar LSTA U.S. B Ratings Loan Index returned 14.64%. The fund's under-performance relative to the benchmark performance was primarily driven by the surge in leveraged loan prices in 2023 which was more prevalent in the index.

The views expressed in this report are exclusively those of Manulife Investment Management Private Markets (US) LLC, and are subject to change. They are not meant as investment advice. Please note that the holdings discussed in this report, if any, may not have been held by the fund for the entire period. Portfolio composition is subject to review in accordance with the fund's investment strategy and may vary in the future. Current and future portfolio holdings are subject to risk.

John Hancock GA Senior Loan Trust

A look at performance

TOTAL RETURNS FOR THE PERIOD ENDED DECEMBER 31, 2023

1From 11-3-20.

Performance figures assume all distributions have been reinvested.

The returns reflect past results and should not be considered indicative of future performance. Investment returns and principal value will fluctuate and a shareholder may sustain losses. Current performance may be higher or lower than the performance cited.

The performance table above and the chart on the next page do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the sale of fund shares. The fund's performance results reflect any applicable fee waivers or expense reductions, without which the expenses would increase and results would have been less favorable.

John Hancock GA Senior Loan Trust

A look at performance

This chart shows what happened to a hypothetical $10,000 investment in John Hancock GA Senior Loan Trust for the periods indicated, assuming all distributions were reinvested. For comparison, we've shown the same investment in the Morningstar LSTA U.S. B Ratings Loan Index.

At net asset value

Morningstar LSTA U.S. B Ratings Loan Index

Ending values 12-31-23

$13,000

$12,344 $12,321

The Morningstar LSTA U.S. B Ratings Loan Index tracks the performance of U.S. leveraged loans in the B rated category.

It is not possible to invest directly in an index. Index figures do not reflect expenses, which would result in lower returns.

The returns reflect past results and should not be considered indicative of future performance.

John Hancock GA Senior Loan Trust

Portfolio summary 12-31-23

Portfolio Composition as of 12-31-23 (% of total investments)

Cash and cash equivalents are not included.

Percentages include unfunded loan commitments.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Portfolio of investments 12-31-23

The percentage shown for each investment category is the total value of the category as a percentage of the net assets of the fund unless otherwise indicated.

^All par values are denominated in U.S. dollars unless otherwise indicated.

Security Abbreviations and Legend

(A)Securities are valued using significant unobservable inputs and are classified as Level 3 in the fair value hierarchy. Refer to Note 2 to the financial statements.

(B)Senior loans are variable rate obligations which generally pay interest rates that are periodically redetermined by reference to a base lending rate and spread, which are both subject to change. The rate shown represents the rate at period end.

(C)Unfunded or partially unfunded loan commitments. The stated interest rate reflects the reference rate and spread of the funded portion, if any. No interest rate is determined for unfunded positions. See Note 2 for more information.

(D)The rate shown is the annualized seven-day yield as of 12-31-23.

At 12-31-23, the aggregate cost of investments for federal income tax purposes was $499,611,102. Net unrealized depreciation aggregated to $1,077,923, of which $3,588,055 related to gross unrealized appreciation and $4,665,978 related to gross unrealized depreciation.

The accompanying notes are an integral part of the financial statements.

Financial statements

John Hancock GA Senior Loan Trust

Statement of assets and liabilities 12-31-23

John Hancock GA Senior Loan Trust

Statement of operations for the year ended 12-31-23

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Statements of changes in net assets

John Hancock GA Senior Loan Trust

Statement of cash flows for the year ended 12-31-23

Cash flows from operating activities

The accompanying notes are an integral part of the financial statements.

John Hancock GA Senior Loan Trust

Financial highlights

1Period from 11-3-20 (commencement of operations) to 12-31-20.

2Based on average daily shares outstanding.

3Not annualized.

4Includes performance fees expense of 1.18%, 0.45%, 0.50% and 0.10% (unannualized) for the periods ended 12-31-23, 12-31-22, 12-31-21 and 12-31-20, respectively.

5Annualized. Certain expenses are presented unannualized.

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

1. Organization

John Hancock GA Senior Loan Trust (the fund) is a Delaware statutory trust that is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as a closed-end management investment company. The investment objective of the fund is to generate current income.

The fund is only offered to "accredited investors" within the meaning of Regulation D under the Securities Act of 1933 (the 1933 Act), non-U.S. investors within the meaning of Regulation S under the 1933 Act, and other investors eligible to invest in a private placement.

2. Significant accounting policies

The financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (US GAAP), which require management to make certain estimates and assumptions as of the date of the financial statements. Actual results could differ from those estimates and those differences could be significant. The fund qualifies as an investment company under Topic 946 of Accounting Standards Codification of US GAAP.

Events or transactions occurring after the end of the fiscal period through the date that the financial statements were issued have been evaluated in the preparation of the financial statements. The following summarizes the significant accounting policies of the fund:

Security valuation. Investments are valued at the end of each month at a minimum. The fund invests primarily in senior loans. Manulife Investment Management Private Markets (US) LLC (the Advisor), assisted by its Pricing Committee (composed of officers of the Advisor and its affiliates), determines the fair value of the fund's securities that are not publicly traded or whose market prices are not readily available pursuant to procedures established by the Advisor and adopted by the Board of Trustees. In connection with that determination, portfolio valuations are prepared in accordance with the Advisor's valuation policy using valuation obtained from independent valuation firms and/or proprietary models.

Valuation techniques include discounted cash flow models, comparison with similar instruments for which observable market prices exist and other valuation models. Assumptions and inputs used in valuation techniques include risk-free and benchmark interest rates, credit spreads and other inputs used in estimating discount rates. For senior loans, the fund uses valuations from independent valuation firms, which are based on models developed from recognized US GAAP valuation approaches under ASC 820. Some or all of the significant inputs into these models may be unobservable and are derived either from observable market prices or rates or are estimated based on unobservable assumptions. Valuation models that employ significant unobservable inputs require a higher degree of management judgment and estimation in the determination of fair value. Judgment and estimation are usually required for the selection of the appropriate valuation model to be used, determination of expected future cash flows on the financial instrument being valued, determination of the probability of counterparty default and prepayments and selection of appropriate discount rates.

The fund uses a three-tier hierarchy to prioritize the pricing assumptions, referred to as inputs, used in valuation techniques to measure fair value. Level 1 includes securities valued using quoted prices in active markets for identical securities. Level 2 includes securities valued using other significant observable inputs. Observable inputs may include quoted prices for similar securities, interest rates, prepayment speeds and credit risk. Prices for securities valued using these inputs are received from independent pricing vendors and brokers and are based on an evaluation of the inputs described. Level 3 includes securities valued using significant unobservable inputs when market prices are not readily available or reliable, including the Advisor's own assumptions in determining the fair value of investments. Factors used in determining value may include market or issuer specific events or trends, changes in interest rates and credit quality. The

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

inputs or methodology used for valuing securities are not necessarily an indication of the risks associated with investing in those securities. Changes in valuation techniques and related inputs may result in transfers into or out of an assigned level within the disclosure hierarchy.

Senior loan investments are measured at fair value based on the present value of the expected cash flows of the loans. There are no quoted prices in active markets. Assumptions and inputs used in the valuation of senior loan investments include prepayment estimates, determination of the discount rate based on the risk-free interest rate adjusted for credit risk (including estimation of probability of default), liquidity and any other adjustments that the independent valuation firm believes that a third-party market participant would take into account in pricing a transaction. Senior loan investment valuations rely primarily on the use of significant unobservable inputs, including credit assumptions, which require significant judgment and, accordingly, are classified as Level 3.

Other debt obligations are typically valued based on the evaluated prices provided by an independent pricing vendor. Independent pricing vendors utilize matrix pricing which takes into account factors such as institutional-size trading in similar groups of securities, yield, quality, coupon rate, maturity, type of issue, trading characteristics and other market data, as well as broker supplied prices. Other debt obligations are generally classified as Level 2.

Investments in open-end mutual funds are valued at their respective net asset values each business day and are generally classified as Level 1.

The following is a summary of the values by input classification of the fund's investments as of December 31, 2023 by major security category or type:

The following is a reconciliation of Level 3 assets for which significant unobservable inputs were used to determine fair value. There were no transfers into or out of Level 3 during the period.

*Change in unrealized appreciation (depreciation) attributable to Level 3 securities held at the period end.

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

The valuation techniques and significant amounts of unobservable inputs used in the fair value measurement of the fund's Level 3 securities are outlined in the table below.

*A weighted average is an average in which each input in the grouping is assigned a weighting before summing to a single average value. The weighting of the input is determined based on a security's fair value as a percentage of the total fair value.

A change to unobservable inputs of the fund's Level 3 securities as of December 31, 2023 could have resulted in changes to the fair value measurement, as follows:

Due to the inherent uncertainty of determining the fair value of Level 3 investments, the fair value of the investments may differ significantly from the values that would have been used had a ready market for such securities existed and may differ materially from the values that may ultimately be received or settled. Further, such investments will generally be subject to legal and other restrictions, or otherwise will be less liquid than publicly traded instruments. If the fund is required to liquidate a portfolio investment in a forced or liquidation sale, the fund might realize significantly less than the value at which such investment will have been previously been recorded. The fund's investments will be subject to market risk. Market risk is the potential for changes in the value due to market changes. Market risk is directly impacted by the volatility and liquidity in the markets in which the investments are traded.

Senior loans. The fund invests in senior loans. Senior loans include first and second lien term loans, delayed draw term loans, and revolving credit facilities. The fund will only invest in loans and commitments that are determined to be below investment-grade. The fund's investment policies are based on credit quality at the time of purchase. Credit quality is determined by the Advisor. The fund may invest in loans with a maturity of up to nine years from the closing date of the loan. The Advisor typically expects to employ a buy-and-hold strategy. The fund may invest in loans either by transacting directly at the initial funding date or acquiring loans in secondary market transactions. The fund may invest in loans secured by substantially all of the assets of the borrower and the other loan parties, subject to customary exceptions, including a pledge of the equity of the borrower and its subsidiaries.

The fund may be subject to greater levels of credit risk, call (or prepayment) risk, settlement risk and liquidity risk than funds that do not invest in senior loans. Senior loans are considered predominantly speculative with respect to an issuer's continuing ability to make principal and interest payments, and may be more volatile than other types of securities. An economic downturn or individual corporate developments could adversely affect the market for these instruments and reduce the fund's ability to sell these instruments at an advantageous time or price. An economic downturn would generally lead to a higher non-payment rate and a senior loan may lose significant value before a default occurs. The fund may also be subject to greater levels of liquidity risk than funds that do not invest in senior loans. In addition, the senior loans in which the fund invests may not be listed on any exchange and a secondary market for such loans may be comparatively less liquid relative to markets for other more liquid fixed income securities. Consequently, transactions in senior loans may involve greater costs than transactions in more actively traded securities. Restrictions on transfers in loan agreements, a lack of publicly-available information, irregular trading activity and wide

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

bid/ask spreads among other factors, may, in certain circumstances, make senior loans difficult to value accurately or sell at an advantageous time or price than other types of securities or instruments. These factors may result in the fund being unable to realize full value for the senior loans and/or may result in the fund not receiving the proceeds from a sale of a senior loan for an extended period after such sale, each of which could result in losses to the fund. Senior loans may have extended trade settlement periods which may result in cash not being immediately available to the fund. If an issuer of a senior loan prepays or redeems the loan prior to maturity, the fund may have to reinvest the proceeds in other senior loans or similar instruments that may pay lower interest rates. Senior loans in which the fund invests may or may not be collateralized, although the loans may not be fully collateralized and the collateral may be unavailable or insufficient to meet the obligations of the borrower. The fund may have limited rights to exercise remedies against such collateral or a borrower, and loan agreements may impose certain procedures that delay receipt of the proceeds of collateral or require the fund to act collectively with other creditors to exercise its rights with respect to a senior loan. Because of the risks involved in investing in senior loans, an investment in the fund should be considered speculative. Junior loans, which are secured and unsecured subordinated loans, second lien loans and subordinate bridge loans, involve a higher degree

of overall risk than senior loans of the same borrower due to the junior loan's lower place in the borrower's capital structure and, in some cases, their unsecured status.

The fund may also enter into, or acquire participations in, delayed funding loans and revolving credit facilities, in which a bank or other lender agrees to make loans up to a maximum amount upon demand by the borrower during a specified term. These commitments may have the effect of requiring the fund to increase its investment in a company at a time when it might not be desirable to do so (including at a time when the company's financial condition makes it unlikely that such amounts will be repaid). Delayed funding loans and revolving credit facilities are subject to credit, interest rate and liquidity risk and the risks of being a lender. Unfunded loan commitments are marked to market in accordance with the fund's valuation policies. Any related unrealized appreciation (depreciation) on unfunded commitments is included in unaffiliated investments, at value in the Statement of assets and liabilities and change in net unrealized appreciation (depreciation) in the Statement of operations. As of December 31, 2023, the fund had the following unfunded commitments outstanding.

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

Security transactions and related investment income. Investment security transactions are accounted for on a trade date plus one basis for NAV calculations. However, for financial reporting purposes, investment transactions are reported on trade date. Interest income is accrued as earned. Interest income includes coupon interest and amortization/accretion of premiums/discounts on debt securities. Debt obligations may be placed in a non-accrual status and related interest income may be reduced by stopping current accruals and writing off interest receivable when the collection of all or a portion of interest has become doubtful. Gains and losses on securities sold are determined on the basis of identified cost and may include proceeds from litigation.

Overdrafts. Pursuant to the custodian agreement, the fund's custodian may, in its discretion, advance funds to the fund to make properly authorized payments. When such payments result in an overdraft, the fund is obligated to repay the custodian for any overdraft, including any costs or expenses associated with the overdraft. The custodian may have a lien, security interest or security entitlement in any fund property that is not otherwise segregated or pledged, to the maximum extent permitted by law, to the extent of any overdraft. Overdrafts at period end, if any, are presented under the caption Due to custodian in the Statements of assets and liabilities.

Line of credit. The fund has entered into a revolving promissory note agreement with John Hancock Funding Company, LLC (JH Funding) and a Line of Credit agreement with John Hancock Life Insurance Company (JHUSA). The aggregate outstanding borrowings under the agreements with JHUSA and JH Funding for the fund will not exceed $50 million. Any borrowings will be first drawn from JHUSA subject to

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

certain conditions as specified in the agreement; otherwise, the borrowings will be drawn from JH Funding. There were no upfront fees or commitment fees paid by the fund in connection with these line of credit agreements. The borrowings under these agreements are designed to be short-term to satisfy intermittent delayed draws and will not be used to originate new loans or for investment leverage. For the year ended December 31, 2023, the fund had no borrowings under the line of credit.

Expenses. Expense estimates are accrued in the period to which they relate and adjustments are made when actual amounts are known.

Statement of cash flows. A Statement of cash flows is presented when a certain percentage of the fund's investments is classified as Level 3 in the fair value hierarchy. Information on financial transactions that have been settled through the receipt and disbursement of cash is presented in the Statement of cash flows. The cash amount shown in the Statement of cash flows is the amount included in the fund's Statement of assets and liabilities and represents the cash on hand at the fund's custodian and does not include any short-term investments.

Federal income taxes. The fund intends to continue to qualify as a regulated investment company by complying with the applicable provisions of the Internal Revenue Code and will not be subject to federal income tax on taxable income that is distributed to shareholders. Therefore, no federal income tax provision is required.

As of December 31, 2023, the fund had no uncertain tax positions that would require financial statement recognition, derecognition or disclosure. The fund's federal tax returns are subject to examination by the Internal Revenue Service for a period of three years.

Distribution of income and gains. Distributions to shareholders from net investment income and net realized gains, if any, are recorded on the ex-date. The fund generally declares and pays dividends at least quarterly. Capital gain distributions, if any, are typically distributed annually.

The tax character of distributions for the years ended December 31, 2023 and 2022 was as follows:

As of December 31, 2023, there were no distributable earnings on a tax basis.

Such distributions and distributable earnings, on a tax basis, are determined in conformity with income tax regulations, which may differ from US GAAP. Distributions in excess of tax basis earnings and profits, if any, are reported in the fund's financial statements as a return of capital.

Capital accounts within the financial statements are adjusted for permanent book-tax differences. These adjustments have no impact on net assets or the results of operations. Temporary book-tax differences, if any, will reverse in a subsequent period. The fund had no material book-tax differences at December 31, 2023.

3. Guarantees and indemnifications

Under the fund's organizational documents, its Officers and Trustees are indemnified against certain liabilities arising out of the performance of their duties to the fund. Additionally, in the normal course of business, the fund enters into contracts with service providers that contain general indemnification clauses. The fund's maximum exposure under these arrangements is unknown, as this would involve future claims that may be made against the fund that have not yet occurred. The risk of material loss from such claims is considered remote.

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

4. Fees and transactions with affiliates

The Advisor serves as investment advisor for the fund. The fund does not have a principal underwriter. The fund has entered into a Placement Agency Agreement with John Hancock Investment Management Distributors LLC (the Distributor), an affiliate of the Advisor, to offer to sell shares of the fund. The Advisor is an indirect wholly-owned subsidiary of Manulife Financial Corporation (MFC), and the Distributor is an indirect, principally owned subsidiary of John Hancock Life Insurance Company (U.S.A.), which in turn is a subsidiary of MFC. Prior to April 20, 2023, the fund had a Placement Agency Agreement with John Hancock Distributors, LLC.

Management fee. The fund has an investment management agreement with the Advisor under which the fund pays an annual fee rate of 0.55% of the fund's average net assets.

Performance fee. The fund has an agreement with the Advisor under which the fund pays a performance fee at annual rate of 10% of the fund's net profits, if any, over the high water mark (as defined below) provided that the performance fee shall be due only if (and, to the extent necessary, shall be reduced by an amount so that), after deducting such performance fee the fund's net profits as of the end of the applicable quarter will at least equal a defined preferred return (as defined below). For the purposes of calculating the performance fee, net profits will be determined by taking into account net realized gain or loss (including realized gain that has been distributed to shareholders during a fiscal quarter and net of fund expenses, including the management fee) and the net change in unrealized appreciation or depreciation of securities positions, as well as dividends, interest and other income. No performance fee will be payable for any fiscal quarter unless losses and depreciation from prior fiscal quarters (the cumulative loss) have been recovered by the fund, which is referred to as a "high water mark" calculation. The cumulative loss to be recovered before payment of performance fees will be reduced in the event of withdrawals by shareholders. The Advisor is under no obligation to repay any performance fees previously paid by the fund. Thus, the payment of performance fee for a fiscal quarter will not be reversed by the subsequent decline of the fund's net asset value in any subsequent fiscal quarter.

The preferred return as of the end of the applicable fiscal quarter is an amount equal to (a) 1.25% (the "preferred return rate") multiplied by (b) the fund's net asset value as of the beginning of the fiscal quarter, adjusted to reflect additions to the fund's net asset value resulting from new share purchases during the fiscal quarter and reductions to the fund resulting from withdrawals by, or distributions to, shareholders during the fiscal quarter (the "preferred return base"). The performance fee will not be payable for any fiscal quarter unless losses and depreciation from prior fiscal quarters have been recovered by the fund. The performance fee is accrued monthly and paid quarterly.

Accounting and legal services. Pursuant to a service agreement, the fund reimburses the Advisor for all expenses associated with providing the administrative, financial, legal, compliance, accounting and recordkeeping services to the fund, including the preparation of all tax returns, periodic reports to shareholders and regulatory reports, among other services. These accounting and legal services fees incurred for the year ended December 31, 2023 amounted to an annual rate of 0.05% of the fund's average net assets.

Trustee expenses. The fund compensates each Trustee who is not an employee of the Advisor or its affiliates.

Co-investment. Pursuant to an Exemptive Order issued by the SEC, the fund is permitted to negotiate certain investments with entities with which it would be restricted from doing so under the 1940 Act, such as the Advisor and its affiliates. The fund is permitted to co-invest with affiliates if certain conditions are met. For example, the Advisor makes an independent determination of the appropriateness of the investment for the fund. Also, a "required majority" (as defined in the 1940 Act) of the fund's independent trustees make certain conclusions in connection with a co-investment transaction as set forth in the order, including that (1)

John Hancock GA Senior Loan Trust

Notes to financial statements 12-31-23

the terms of the transactions, including the consideration to be paid, are reasonable and fair to the fund and shareholders and do not involve overreaching by the fund or shareholders on the part of any person concerned and (2) the transaction is consistent with the interests of shareholders and is consistent with the fund's investment objective and strategies. During the year ended December 31, 2023, commitments entered into by the fund pursuant to the exemptive order amounted to $213,507,247, including unfunded commitments of $75,807,708.

5. Fund share transactions

Affiliates of the fund owned 100% of shares of the fund on December 31, 2023.

6. Purchase and sale of securities

Purchases and sales of securities, other than short-term investments, amounted to $231,935,352 and $159,830,495, respectively, for the year ended December 31, 2023.

7. LIBOR discontinuation risk

Certain debt securities, derivatives and other financial instruments have traditionally utilized LIBOR as the reference or benchmark rate for interest rate calculations. However, following allegations of manipulation and concerns regarding liquidity, the U.K. Financial Conduct Authority (UK FCA) announced that LIBOR would be discontinued as of June 30, 2023. The UK FCA elected to require the ICE Benchmark Administration Limited, the administrator of LIBOR, to continue publishing a subset of British pound sterling and U.S. dollar LIBOR settings on a "synthetic" basis. The synthetic publication of the three-month sterling LIBOR will continue until March 31, 2024, and the publication of the one-, three and six-month U.S. dollar LIBOR will continue until September 30, 2024.

Although the transition process away from LIBOR has become increasingly well-defined in advance of the discontinuation dates, the impact on certain debt securities, derivatives and other financial instruments remains uncertain. Market participants have adopted alternative rates such as Secured Overnight Financing Rate (SOFR) or otherwise amended financial instruments referencing LIBOR to include fallback provisions and other measures that contemplated the discontinuation of LIBOR or other similar market disruption events, but neither the effect of the transition process nor the viability of such measures is known. To facilitate the transition of legacy derivatives contracts referencing LIBOR, the International Swaps and Derivatives Association, Inc. launched a protocol to incorporate fallback provisions. However, there are obstacles to converting certain longer term securities and transactions to a new benchmark or benchmarks and the effectiveness of one alternative reference rate versus multiple alternative reference rates in new or existing financial instruments and products has not been determined. Certain proposed replacement rates to LIBOR, such as SOFR, which is a broad measure of secured overnight U.S. Treasury repo rates, are materially different from LIBOR, and changes in the applicable spread for financial instruments transitioning away from LIBOR will need to be made to accommodate the differences.

The utilization of an alternative reference rate, or the transition process to an alternative reference rate, may adversely affect the fund's performance.

8. New accounting pronouncement

In March 2020, the Financial Accounting Standards Board (FASB) issued an Accounting Standards Update (ASU), ASU 2020-04, which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the LIBOR and other IBOR-based reference rates as of the end of 2021. The temporary relief provided by ASU 2020-04 is effective for certain reference rate-related contract modifications that occur during the period March 12, 2020 through December 31, 2024. Management expects that the adoption of the guidance will not have a material impact to the financial statements.

John Hancock GA Senior Loan Trust

Tax information

Unaudited

For federal income tax purposes, the following information is furnished with respect to the distributions of the fund, if any, paid during its taxable year ended December 31, 2023.

The fund reports the maximum amount allowable as Section 163(j) Interest Dividends.

The fund paid $1,099,247 in long term capital gain dividends.

Qualified Interest Income (QII)

NonResident Alien (NRA) shareholders are normally subject to a 30% (or lower tax treaty rate depending on the country) NRA withholding tax on income and short-term capital gain dividends paid by a mutual fund, unless such dividends are designated as qualified interest income or qualified short-term capital gains, and therefore exempt from NRA withholding tax. Under the American Jobs Creation Act of 2004, the following percentages of ordinary dividends paid during the fiscal year ended December 31, 2023 are considered to be derived from "qualified interest income," as defined in Section 871(k)(1)(E) of the Code.

John Hancock GA Senior Loan Trust

Investment objective, principal investment strategies, and principal risks (unaudited)

Recent Changes

The following information in this annual report is a summary of certain changes since December 31, 2022. This information may not reflect all of the changes that have occurred since you purchased shares of the fund.

Changes to Principal Investment Strategies Approved by the Board

On March 2, 2023, the Board of Trustees approved changes to the fund's principal investment strategies. In this regard, the fund's principal investment strategy disclosure has been revised to clarify that the fund may borrow money or leverage its investments for the purposes of funding investments in instances of short term liquidity needs.

Investment Objective

The fund's investment objective is to generate current income.

Principal Investment Strategies

Under normal market conditions, the fund will invest at least 80% of its net assets (plus any borrowings for investment purposes) in senior loans. Senior loans include first and second lien term loans, delayed draw term loans, and revolving credit facilities. Senior loans do not include commercial mortgage loans (including subordinated real estate mezzanine financing). The fund will only invest in loans and commitments that are determined to be below investment-grade. The fund's investment policies are based on credit quality at the time of purchase. Credit quality is determined by the Advisor. The fund may invest in loans with a maturity of up to nine years from the closing date of the loan. The Advisor typically expects to employ a buy-and-hold strategy. The fund may invest in loans either by transacting directly at the initial funding date or acquiring loans in secondary market transactions.

The fund may invest in loans secured by substantially all of the assets of the borrower and the other loan parties (subject to customary exceptions), including a pledge of the equity of the borrower and its subsidiaries. While real property is not a primary source of collateral, occasionally mortgages are part of the collateral package if the borrower owns particularly valuable real property. The fund may also invest in subordinated debt obligations to the extent permitted by the fund's investment restrictions.

The Advisor undertakes a comprehensive due diligence process, which includes a credit review and internal loan rating process as well as review of loan terms and collateral. The Advisor does not intend to cause the fund to borrow money or leverage its investments for the purpose of funding investments, other than in instances of short-term liquidity needs, and paying fund expenses.

Principal Risks

An investment in the fund is subject to investment and market risks, including the possible loss of the entire principal invested.

The fund's main risks are listed below in alphabetical order, not in order of importance.

Changing distribution level & return of capital risk. There is no guarantee prior distribution levels will be maintained, and distributions may include a substantial tax return of capital. A return of capital is the return of all or a portion of a shareholder's investment in the fund.

Credit and counterparty risk. The issuer or guarantor of a fixed-income security may not make timely payments or otherwise honor its obligations. A downgrade or default affecting any of the fund's securities could affect the fund's performance.

John Hancock GA Senior Loan Trust

Investment objective, principal investment strategies, and principal risks (unaudited)

Delayed funding loans and revolving credit facilities risk. Delayed funding loans and revolving credit facilities may have the effect of requiring the fund to increase its investment in a company at a time when it might not be desirable to do so (including at a time when the company's financial condition makes it unlikely that such amounts will be repaid). Delayed funding loans and revolving credit facilities are subject to credit, interest rate and liquidity risk and the risks of being a lender.

Economic and market events risk. Events in the U.S. and global financial markets, including actions taken by the U.S. Federal Reserve or foreign central banks to stimulate or stabilize economic growth, may at times result in unusually high market volatility, which could negatively impact performance. Reduced liquidity in credit and fixed-income markets could adversely affect issuers worldwide. Financial Institutions could suffer losses as interest rates rise or economic conditions deteriorate.

Fixed-income securities risk. A rise in interest rates typically causes bond prices to fall. The longer the average maturity or duration of the bonds held by a fund, the more sensitive it will likely be to interest-rate fluctuations. An issuer may not make all interest payment or repay all or any of the principal borrowed.

Changes in a security's credit quality may adversely affect fund performance. Additionally, the value of inflation-indexed securities is subject to the effects of changes in market interest rates caused by factors other than inflation (real interest rates). Generally, when real interest rates rise, the value of inflation-indexed securities will fall and the fund's value may decline as a result of this exposure to these securities.

Illiquid and restricted securities risk. Illiquid and restricted securities may be difficult to value and may involve greater risks than liquid securities. Illiquidity may have an adverse impact on a particular security's market price and the fund's ability to sell the security.

LIBOR discontinuation risk.The official publication of the London Interbank Offered Rate (LIBOR), which many debt securities, derivatives and other financial instruments traditionally utilized as the reference or benchmark rate for interest rate calculations, was discontinued as of June 30, 2023. However, a subset of British pound sterling and U.S. dollar LIBOR settings will continue to be published on a ￿synthetic￿ basis. The synthetic publication of the three-month sterling LIBOR will continue until March 31, 2024, and the publication of the one-, three- and six-month U.S. dollar LIBOR will continue until September 30, 2024. The discontinuation of LIBOR and a transition to replacement rates may lead to volatility and illiquidity in markets and may adversely affect the fund's performance.

Liquidity risk. The extent (if at all) to which a security may be sold without negatively impacting its market value may be impaired by reduced market activity or participation, legal restrictions, or other economic and market impediments. Liquidity risk may be magnified in rising interest rate environments due to higher than normal redemption rates. Widespread selling of fixed-income securities to satisfy redemptions during periods of reduced demand may adversely impact the price or salability of such securities.

Loan participations risk. Participations and assignments involve special types of risks, including credit risk, interest rate risk, liquidity risk, and the risks of being a lender. Investments in loan participations and assignments present the possibility that a fund could be held liable as a co-lender under emerging legal theories of lender liability. If a fund purchases a participation, it may only be able to enforce its rights through the lender and may assume the credit risk of the lender in addition to the borrower.

Lower-rated and high-yield fixed-income securities risk. Lower-rated and high-yield fixed-income securities (junk bonds) are subject to greater credit quality risk, risk of default, and price volatility than higher-rated fixed-income securities, may be considered speculative, and can be difficult to resell.

Operational and cybersecurity risk. Cybersecurity breaches may allow an unauthorized party to gain access to fund assets, customer data, or proprietary information, or cause a fund or its service providers to suffer data corruption or lose operational functionality. Similar incidents affecting issuers of a fund's securities may negatively impact performance. Operational risk may arise from human error, error by third parties, communication errors, or technology failures, among other causes.

John Hancock GA Senior Loan Trust

Investment objective, principal investment strategies, and principal risks (unaudited)

Senior loans risk. Senior loans may be comparatively less liquid relative to markets for other more liquid fixed income securities. Restrictions on transfers in loan agreements, a lack of publicly-available information, irregular trading activity and wide bid/ask spreads among other factors, may, in certain circumstances, make senior loans difficult to value accurately or sell at an advantageous time or price than other types of securities or instruments. Senior loans may have extended trade settlement periods which may result in cash not being immediately available. If an issuer of a senior loan prepays or redeems the loan prior to maturity, the fund may have to reinvest the proceeds in other senior loans or similar instruments that may pay lower interest rates. Senior loans in which the fund invests may or may not be collateralized, although the loans may not be fully collateralized and the collateral may be unavailable or insufficient to meet the obligations of the borrower. The fund may have limited rights to exercise remedies against such collateral or a borrower, and loan agreements may impose certain procedures that delay receipt of the proceeds of collateral or require the fund to act collectively with other creditors to exercise its rights with respect to a senior loan.

Subordinated liens on collateral risk. Certain debt investments that the fund may make will be secured on a second priority basis by the same collateral securing senior secured debt of such companies. The first priority liens on the collateral will secure the fund's obligations under any outstanding senior debt and may secure certain other future debt that may be permitted to be incurred by the fund under the agreements governing the debt. The holders of obligations secured by the first priority liens on the collateral will generally control the liquidation of and be entitled to receive proceeds from any realization of the collateral to repay their obligations in full before the fund is so entitled. There can be no assurance that the proceeds, if any, from the sale or sales of all of the collateral would be sufficient to satisfy the debt obligations secured by the second priority liens after payment in full of all obligations secured by the first priority liens on the collateral.

John Hancock GA Senior Loan Trust

Board considerations (unaudited)

EVALUATION OF ADVISORY AGREEMENT BY THE BOARD OF TRUSTEES

This section describes the evaluation by the Board of Trustees (the Board) of John Hancock Senior Loan Trust (the fund) of the Advisory Agreement between the fund and Manulife Investment Management Private Markets (US) LLC (the Advisor) (the Advisory Agreement). The Advisory Agreement was re-approved for an annual period at an in-person meeting on October 11, 2023. The Trustees who are not "interested persons" of the Trust as defined by the Investment Company Act of 1940, as amended (the 1940 Act) (the Independent Trustees) also met separately with counsel to the Independent Trustees to evaluate and discuss the information presented.

Continuation of Advisory Agreement

At an in-person meeting held on October 11, 2023, the Board, including all of the Independent Trustees, re-approved for an annual period the continuation of the Advisory Agreement. In considering the Advisory Agreement, the Board received in advance of the meeting a variety of materials relating to the fund and the Advisor, including, to the extent available, comparative performance (including performance information for an applicable benchmark index, aggregate performance information for commercial real estate whole loan providers), fee and expense information for other comparable investment companies, information regarding the Advisor's revenues and costs of providing services to the fund and any compensation paid to affiliates of the Advisor, and other information provided by the Advisor regarding the nature, extent, and quality of services provided by the Advisor under the Advisory Agreement. The information received and considered by the Board in connection with the October meeting was both written and oral. The Board also considered the nature, quality, and extent of the non-advisory services, if any, provided to the fund by the Advisor's affiliates. Throughout the process, the Board asked questions of and were afforded the opportunity to request additional information from management. The Board is assisted by counsel for the fund and the Independent Trustees are also separately assisted by independent legal counsel throughout the process. The Independent Trustees also received a memorandum from their independent legal counsel discussing the legal standards for their consideration of the proposed continuation of the Advisory Agreement and discussed the proposed continuation of the Advisory Agreement in private sessions with their independent legal counsel at which no representatives of management were present.

In approving the continuation of the Advisory Agreement, the Board, including the Independent Trustees, considered a variety of factors, including those discussed below. The Board also considered other market and economic factors and did not treat any single factor as determinative, and each Trustee may have attributed different weights to different factors. The Board noted that, at the meeting when the renewal of the Advisory Agreement is considered, particular focus is given to information concerning fund performance, comparability of fees and total expenses, and profitability. However, the Board noted that the evaluation process with respect to the Advisor is an ongoing one. In this regard, the Board also took into account discussions with management and information provided to the Board at prior meetings with respect to the services provided by the Advisor to the fund, including quarterly performance reports prepared by management containing reviews of investment results and prior presentations with respect to the fund.

Nature, extent and quality of services. Among the information received by the Board from the Advisor relating to the nature, extent and quality of services provided to the fund, the Board reviewed information provided by the Advisor relating to its operations and personnel, descriptions of its organizational and management structure, and information regarding the Advisor's compliance and regulatory history, including its Form ADV. The Board also noted that on a regular basis it receives and reviews information from the Trust's Chief Compliance Officer (CCO) regarding the fund's compliance policies and procedures established pursuant to Rule 38a-1 under the 1940 Act. The Board observed that the scope of services provided by the Advisor, and of the undertakings required of the Advisor in connection with those services, including maintaining and monitoring its own and the fund's compliance programs, risk management and other programs, and cybersecurity programs, had expanded over time as a result of regulatory, market and

John Hancock GA Senior Loan Trust

Board considerations (unaudited)

other developments. The Board considered that the Advisor is responsible for the management of the day-to-day operations of the fund, and for monitoring and reviewing the activities of third-party service providers. The Board also considered the significant risks assumed by the Advisor in connection with the services provided to the fund including investment, operational, enterprise, regulatory and compliance risks.

In considering the nature, extent, and quality of the services provided by the Advisor, the Trustees also took into account their knowledge of the Advisor's management and the quality of the performance of the Advisor's duties, through Board meetings, discussions and reports during the preceding year and through each Trustee's experience as a Trustee of the Trust and of the other trusts in the John Hancock group of funds complex (the John Hancock Fund Complex).

In the course of their deliberations regarding the Advisory Agreement, the Board considered, among other things:

(a)the skills and competency with which the Advisor has in the past managed the Trust's affairs;

(b)the background, qualifications, and skills of the Advisor's personnel;

(c)the Advisor's compliance policies and procedures and its responsiveness to regulatory changes and fund industry developments;

(d)the Advisor's administrative capabilities, including its ability to supervise the other service providers for the fund;

(e)the financial condition of the Advisor and whether it has the financial wherewithal to continue to provide a high level and quality of services to the fund;

(f)the Advisor's initiatives intended to improve various aspects of the fund's operations; and

(g)the Advisor's reputation and experience in serving as an investment advisor to the Trust.

The Board concluded that the Advisor may reasonably be expected to continue to provide a high quality of services under the Advisory Agreement with respect to the fund.

Investment performance. In considering the fund's performance, the Board noted that it reviews at its regularly scheduled meetings information about the fund's performance results. In connection with the consideration of the Advisory Agreement, the Board:

(a)reviewed information prepared by management regarding the fund's performance;

(b)considered the comparative performance of an applicable benchmark index;

(c)considered the performance of comparable funds, as included in the report prepared by an independent third-party provider of fund data; and

(d)took into account the Advisor's analysis of the fund's performance and its plans and recommendations regarding the fund's advisory arrangement generally.

The Board noted that while it found the comparative data provided by the independent third-party generally useful it recognized its limitations, including in particular that the data may vary depending on the end date selected and the results of the performance comparisons may vary depending on the selection of the peer group and the strategies and fund structures of the peers selected. In this regard, the Board considered that management represented that it believes there are no investment companies clearly comparable to the fund. The Board noted that the fund outperformed its peer group median for the one-year and two-year periods ended June 30, 2023, but underperformed its peer group median for the quarter-to-date and year-to-date periods ended June 30, 2023. The Board noted that the Fund underperformed its benchmark index for the quarter-to-date, year-to-date, one-year and two-year periods ended June 30, 2023. The Board took into account management's discussion of the factors that contributed to the fund's underperformance relative to

John Hancock GA Senior Loan Trust

Board considerations (unaudited)

its peer group for the quarter-to-date and year-to-date periods ended June 30, 2023, and relative to its benchmark for the quarter-to-date, year-to-date, one-year and two-year periods. The Board concluded that the fund's performance is being monitored and reasonably addressed, where appropriate.

The Board concluded that the fund's performance is being monitored and reasonably addressed, where appropriate.

Fees and Expenses. The Board reviewed comparative information regarding the fund's fees and expenses, including, among other data, the fund's management fees and net total expenses as compared to other comparable investment companies. The Board considered that the management fees were higher than the median advisory fees, and the net total expenses were lower than the median advisory fees across the universe of closed-end, interval funds presented and with respect to categories of closed-end interval funds that most closely align with the fund's investment strategy. The Board noted that the peer group was imperfect given the unique investment strategy and structure of the Fund. The Board took into account management's discussion of the fund's expenses. The Board reviewed information provided by the Advisor concerning investment advisory fees charged to other clients having similar investment mandates, if any. The Board considered any difference between the Advisor's services to the fund and the services they provide to other such comparable clients or funds.

The Board concluded that the advisory fees paid by the fund are reasonable in light of the nature, extent and quality of the services provided to the fund under the Advisory Agreement.

Profitability/Fall Out Benefits. In considering the costs of the services provided and the profits realized by the Advisor and its affiliates from the Advisor's relationship with the fund, the Board:

(a)reviewed financial information of the Advisor;

(b)considered that the Advisor will also provide administrative services to the fund on a cost basis pursuant to a services agreement;

(c)noted that affiliates of the Advisor will provide placement agency services to the fund;

(d)noted that the Advisor will derive reputational and other indirect benefits from providing advisory services to the fund;

(e)considered that the Advisor should be entitled to earn a reasonable level of profits in exchange for the level of services it will provide to the fund and the risks that it assumes as Advisor, including entrepreneurial, operational, reputational, and regulatory risk; and

(f)reviewed and considered information presented by the Advisor regarding the net profitability to the Advisor and its affiliates with respect to the fund.

Economies of Scale. In considering the extent to which the fund realizes any economies of scale and whether the fee level reflects these economies of scale for the benefit of the fund's shareholders, the Board took into account management's discussions of the current advisory fee structure, and, as noted above, the services the Advisor provides in performing its functions under the Advisory Agreement. In considering the extent to which economies of scale would be realized if the fund grows and whether the fee level reflects these economies of scale, the Board: (a) reviewed the fund's advisory fee structure and took into account management's discussion of the fund's advisory fee structure; and (b) also considered the potential effect of the fund's future growth in size on its performance and fees.

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John Hancock GA Senior Loan Trust

Board considerations (unaudited)

Based on the Board's evaluation of all factors that the Board deemed to be material, including those factors described above, and assisted by the advice of independent legal counsel, the Board, including the Independent Trustees, concluded that continuation of the Advisory Agreement would be in the best interest of the fund and its shareholders. Accordingly, the Board, and the Independent Trustees voting separately, approved the Advisory Agreement for an additional one-year period.

John Hancock GA Senior Loan Trust

Trustees and Officers

This chart provides information about the Trustees and Officers who oversee the Fund. Officers elected by the Trustees manage the day-to-day operations of the Fund and executed policies formulated by the Trustees.

Cambridge, Massachusetts (2011–2023); Board of Directors, Amwell Corporation (since 2020); Board of Directors, Massachusetts Women's Forum (2018-2020); Board of Directors, National Association of Corporate Directors/New England

(2015-2020); Chief Executive Officer, American Red Cross of Massachusetts Bay (2002–2011); Board of Directors of Eastern Bank Corporation (since 2001); Board of Directors of Eastern Bank Charitable Foundation (since 2001); Board of Directors of Boston Stock Exchange (2002–2008); Board of Directors of Harvard Pilgrim Healthcare (health benefits company) (2007–2011). Trustee of various trusts within the John Hancock Fund Complex (since 2008).

John Hancock GA Senior Loan Trust

Trustees and Officers

The business address for all Trustees and Officers is 197 Clarendon Street, Boston, Massachusetts 02116.

1Each Trustee holds office until his or her successor is elected and qualified, or until the Trustee's death, retirement, resignation, or removal.

2Member of the Audit Committee.

3The Trustee is a Non-Independent Trustee due to current positions with the Advisor and certain affiliates.

John Hancock GA Senior Loan Trust

More information

The fund's proxy voting policies and procedures, as well as the fund proxy voting record for the most recent twelve month period ended June 30, are available free of charge on the Securities and Exchange Commission (SEC) website at sec.gov.

All of the fund's holdings as of the end of the third month of every fiscal quarter are filed with the SEC on Form N-PORT within 60 days of the end of the fiscal quarter. The fund's Form N-PORT filings are available on the SEC's website, sec.gov.