Taxable equivalent net interest income was $25.1 million for the third quarter of 2021, compared to $22.1 million for the third quarter of 2020. Taxable equivalent net interest margin decreased to 2.69% for the three months ended September 30, 2021, from 3.14% for the three months ended September 30, 2020. The margin decrease for the third quarter of 2021 compared to the same period in 2020 was primarily due to the increase in deposits and corresponding increase in low-yielding cash balances. For the nine months ended September 30, 2021, taxable equivalent net interest income was $74.9 million compared to $65.3 million for the same period of 2020. Taxable equivalent net interest margin decreased to 2.80% for the nine months ended September 30, 2021, from 3.25% for the nine months ended September 30, 2020. The margin decrease for the first nine months of 2021 compared to the same period in 2020 was primarily due to lower rates on loans resulting from federal funds rate decreases during 2020 and the increase in deposits and corresponding increase in cash balances, which contributed to the margin decline.
The CARES Act and applicable extensions provide relief to borrowers, including the opportunity to defer loan payments while not negatively affecting their credit standing and also provide funding opportunities for small businesses under the PPP from approved SBA lenders. For commercial and consumer customers, we have provided a host of relief options, including payment deferrals (including maturity extensions), loan covenant waivers and low interest rate loan products. Outstanding PPP loans were $48.3 million at September 30, 2021, a decrease of $143.9 million, or 75%, from December 31, 2020. The decrease was due to the forgiveness of $243.0 million in PPP loans during the nine months ended September 30, 2021, offset by the origination of 291 round two PPP loans totaling $73.0 million during the first half of 2021.
We recorded negative provision for credit losses for the quarter ended September 30, 2021, totaling $2.4 million, a decrease of $2.4 million from the quarter ended September 30, 2020, as a result of improved CECL economic forecasts and positive credit quality migration lowering the allowance, partially offset by loan growth during the third quarter of 2021. For the nine months ended September 30, 2021, we recorded negative provision for credit losses totaling $7.9 million, a decrease of $24.8 million from the nine months ended September 30, 2020, primarily due to improved CECL economic forecasts and credit upgrades, partially offset by loan growth during the first nine months of 2021.
Noninterest income increased $2.1 million, or 84%, to $4.6 million from the third quarter of 2020. The increase was primarily due to an increase of $548,000, or 45%, in service charges due to continued growth in our payments, fintech and private capital solutions businesses and a $383,000, or 43%, increase in SBA lending activities resulting from higher SBA premiums in the secondary market. Also contributing to the increase in noninterest income for the third quarter of 2021 was the receipt of SBIC distributions totaling $930,000 in September 2021, which was recorded in other noninterest income.
For the first nine months of 2021, noninterest income increased $4.5 million, or 62%, to $11.8 million. The increase was primarily due to an increase of $1.6 million, or 79%, in SBA lending activities, an increase of $1.6 million, or 46%, in income from service charges and the aforementioned SBIC distributions of $930,000.
For the third quarter of 2021, noninterest expense increased $1.3 million, or 10%, to $15.0 million compared to the third quarter of 2020. The most significant components of the increase were $2.9 million of merger-related expenses, increases of $1.4 million, or 16%, in salaries and employee benefits expense, $265,000 in FDIC premiums, and $175,000, or 31%, in professional services. Salaries and employee benefits expense in the third quarter of 2021 included an increase in short-term and long-term incentive costs of $1.1 million, or 78%, compared to the third quarter of 2020. Partially offsetting the increase in noninterest expense was an employee retention payroll tax credit pursuant to the CARES Act totaling $3.0 million.
Noninterest expense totaled $45.4 million for the nine months ended September 30, 2021, compared to $39.5 million for the same period in 2020. The most significant component of the increase was a $5.3 million, or 20%, increase in salaries and employee benefits primarily related to higher incentives, SBA commissions and $255,000 in contract labor expense for PPP round two loan processing. The first nine months of 2021 included an increase in short-term and long-term incentive costs of $3.6 million, or 95%, along with the partial impact of new hires and merit increases. Also contributing to the increase in noninterest expense were merger-related expenses of $2.9 million and an increase of $786,000 in FDIC premiums resulting from overall asset growth in 2021. Partially offsetting the increase in noninterest expense for the nine months ended September 30, 2021, compared to the same period in 2020 was an employee retention payroll tax credit pursuant to the CARES Act totaling $3.0 million.