million due to loan growth, improved credit quality and the reversal of previous COVID-related asset quality qualitative adjustments.
Noninterest income for the three months ended September 30, 2022 was $3.3 million, a $0.1 million decrease from $3.4 million for the three months ended September 30, 2021. The decline was due to reduced wealth management fees, which are based on account valuations and have been negatively impacted by stock market fluctuations, as well as mortgage banking revenue which has declined due to lower originations and volumes of mortgages sold into the secondary market as the interest rates on mortgages have risen.
Noninterest expense increased $1.8 million or 12.6% to $15.9 million for the three months ended September 30, 2022, from $14.1 million for the three months ended September 30, 2021. Salaries and employee benefits increased $0.6 million or 8.2% due to annual merit increases and the addition of lending teams and credit support staff in our newest expansion markets of Piscataway, New Jersey and Pittsburgh, Pennsylvania that opened during the fourth quarter of 2021. Occupancy and equipment expenses were higher by $0.7 million in the current period due to information technology investments related in part to mobile/digital banking solutions implemented during the second half of 2021.
The provision for income tax expense increased $0.2 million for the three months ended September 30, 2022 compared to the year ago period due to higher taxable income in the current period.
Nine-Month Results – Comparison to Prior Year First Nine Months
Calculated on a fully taxable equivalent basis (“FTE”), a non-GAAP measure1, the net interest margin for the nine months ended September 30, 2022 was 3.04%, a decrease of 2 basis points over the prior year’s period of 3.06%. Excluding the impact of PPP loan interest and net fees, the net interest margin increased to 3.00% in the current period from 2.95% in the year ago period. Tax-equivalent net interest income, a non-GAAP measure1, for the nine months ended September 30, increased $8.6 million or 13.4% to $72.7 million in 2022 from $64.1 million in 2021. The increase in net interest income was driven by an increase in average earning assets of $400.0 million, partially offset by a negative rate variance, and higher funding costs due to an increase of $295.0 million in average interest-bearing liabilities and higher interest rates. The 2022 period included $1.7 million in SBA PPP interest and fees, a decrease of $4.6 million compared to the $6.3 million in the year ago period. Average loans increased $272.4 million and investments increased $304.5 million compared to September 30, 2021. The yield on earning assets was 3.39% for the first nine months of 2022 compared to 3.41% in 2021. The cost of interest bearing liabilities during the nine month period fell slightly to 0.49% from 0.50% a year ago.
For the nine months ended September 30, 2022, the provision for loan losses was $1.7 million, primarily the result of $340.7 million growth of non-PPP loans. For the nine months ended September 30, 2021, there was no provision for loan losses due to improved credit quality and reversal of COVID related asset quality adjustments made in the prior year’s period.
Noninterest income for the nine months ended September 30, 2022 was $10.6 million, a $0.3 million increase from $10.3 million for the nine months ended September 30, 2021. During the period, service charges, fees and commissions increased $0.7 million due in part to the reversal of an accrual of a $0.3 million bank owned life insurance benefit in the year ago period, higher consumer and commercial deposit service charges and higher revenue related to debit card activity. Mortgage banking income decreased $0.4 million during the nine months ended September 30, 2022 compared to the prior year on lower sales volumes.
Noninterest expense for the nine months ended September 30, 2022, was $45.7 million, an increase of $5.5 million from $40.2 million for the prior year’s period. The increase was due primarily to $2.7 million in higher salaries and benefits expense due to annual merit increases, our investment into our newest expansion markets and lower deferred loan origination costs, which are recorded as a contra-salary expense. Occupancy and equipment expenses were higher by $2.2 million in the current period due to information technology investments related to mobile/digital banking solutions implemented during the second half of 2021 and additional costs related to entrance into the Piscataway, New Jersey and Pittsburgh, Pennsylvania markets. Other expenses, which include professional, consulting and loan processing fees, accounted for an increase of $0.4 million.
The provision for income taxes for the nine months ended September 30, 2022 decreased $0.3 million and the effective tax rate was 16.2% as compared to 17.7% in the prior period. The lower effective tax rate in 2022 was due to a $0.6 million deferred tax adjustment recorded in 2021 and higher levels of tax-exempt income in the current period.