Interest income on other interest-bearing deposits, comprised primarily of certificates of deposit in other financial institutions, overnight deposits and stock in the Federal Home Loan Bank, decreased $11,000, or 10.1%, for the three months ended December 31, 2023, due to a decrease in the average balance of $2.7 million, partially offset by an increase in the average yield of 78 basis points, to 4.69% for the three months ended December 31, 2023 from 3.91% for the three months ended December 31, 2022. The increase in average yield was due to the increase in interest rates in the overall economy during the periods.
Interest Expense. Total interest expense increased $440,000, or 788.5%, to $496,000 for the three months ended December 31, 2023 from $56,000 for the three months ended December 31, 2022. Interest expense on deposits increased $281,000, or 578.2%, due primarily to an increase of 101 basis points in the average cost of deposits to 1.18% for the three months ended December 31, 2023 from 0.17% for the three months ended December 31, 2022, which was partially offset by a decrease of $2.9 million, or 2.5%, in the average balance of interest-bearing deposits to $111.5 million for the three months ended December 31, 2023 from $114.4 million for the three months ended December 31, 2022.
Interest expense on borrowings increased $159,000, or 2,206%, for the three months ended December 31, 2023, compared to the three months ended December 31, 2022. The increase was due to a 418 basis point increase in the weighted-average rate, to 5.11% for the three months ended December 31, 2023 and a $10.0 million increase in the average balance outstanding, to $13.0 million for the three months ended December 31, 2023 from $3.0 million for the three months ended December 31, 2022.
Net Interest Income. Net interest income increased $44,000, or 3.3%, to $1.4 million for the three months ended December 31, 2023 compared to $1.3 million for the three months ended December 31, 2022. The increase reflected an increase in the net interest margin to 3.74% for the three months ended December 31, 2023 from 3.71% for the three months ended December 31, 2022, while the average net interest earning assets decreased $3.5 million year to year. The net interest margin was impacted by a series of interest rate increases in the economy during 2023 and 2022.
Provision for Credit Losses. Based on an analysis of the factors described in “Critical Accounting Policies—Allowance for Credit Losses,” management determined that a provision for credit losses was not required for either of the three month periods ended December 31, 2023 and 2022. The allowance for credit losses was $967,000 at December 31, 2023 and $934,000 at September 30, 2023 and represented 0.70% of total loans at both December 31, 2023 and September 30, 2023. The increase in the allowance for credit losses during the three months ended December 31, 2023, was due to the adoption of ASU 2016-13 effective October 1, 2023, which resulted in an increase of $32,000 to the allowance. The determination over the adequacy of the allowance for credit losses was due primarily to the low balances of nonperforming loans, delinquent loans and no net charge-offs in both periods.
Total nonperforming loans were $477,000 at December 31, 2023, compared to $350,000 at September 30, 2023. Classified loans totaled $477,000 at December 31, 2023, compared to $350,000 at September 30, 2023, and total loans past due greater than 30 days were $1.3 million and $830,000 at those respective dates. As a percentage of nonperforming loans, the allowance for credit losses was 195.7% at December 31, 2023 compared to 281.2% at September 30, 2023.
The allowance for credit losses reflects the estimate management believes to be appropriate to cover inherent credit losses in the loan portfolio at December 31, 2023 and 2022. While management believes the estimates and assumptions used in the determination of the adequacy of the allowance are reasonable, such estimates and assumptions could be proven incorrect in the future, and the actual amount of future provisions may exceed the amount of past provisions, and the increase in future provisions that may be required may adversely impact the Bank’s financial condition and results of operations.
Non-Interest Income. Non-interest income totaled $162,000 for the three months ended December 31, 2023, an increase of $34,000, or 26.9%, from the three months ended December 31, 2022. The increase was due primarily to a $22,000, or 87.9%, increase in late charges and fees on loans, an $8,000 nonrecurring loss on sale of investments in the 2022 quarter and a $7,000, or 9.7%, increase in service fees on deposits.