The provision for credit losses on loans increased by $365,000, from $545,000 for the quarter ended September 30, 2022 to $910,000 for the current quarter. The provision for credit losses on loans increased $360,000, from $1.1 million for the nine months ended September 30, 2022 to $1.5 million for the nine months ended September 30, 2023. The increase to the provision for both the three and nine months ended September 30, 2023 was primarily attributable to an increase in loan balances and increased charge-offs.
Net charge-offs increased $163,000 from $222,000 for the third quarter of 2022 to net charge-offs of $385,000 for the third quarter of 2023. Net charge-offs increased $1.2 million from $179,000 for the first nine months of 2022 to $1.4 million for the first nine months of 2023. Year-to-date, the increase was primarily due to a $710,000 charge-off of one commercial loan in the second quarter of 2023 and increased charge-offs in indirect automobile loans of $794,000. The percentage of overdue account balances to total loans decreased to 1.91% as of September 30, 2023 from 2.29% as of December 31, 2022, while non-performing assets increased $404,000, or 9.1%, to $4.8 million at September 30, 2023.
Non-interest income totaled $1.6 million for the three months ended September 30, 2023, an increase of $257,000, or 18.5%, from the comparable period in the prior year, due primarily to a $218,000 gain on life insurance and an increase in investment advisory income. The increase was partially offset by a decrease in the net gain on sales of mortgage loans of $117,000 as activity decreased due to fewer originations in the increasing interest rate environment and a strategic decision to hold new production in our portfolio instead of selling these loans.
Non-interest income totaled $4.4 million for the nine months ended September 30, 2023, a decrease of $223,000, or 4.8%, from the comparable period in the prior year, due primarily to a decrease in the net gain on sales of mortgage loans as activity decreased due to fewer originations in the increasing interest rate environment and a strategic decision to hold new production in our portfolio instead of selling these loans. Gain on sales of mortgage loans decreased $748,000, or 89.0%, compared to the prior year period as we sold $3.7 million of residential mortgage loans in the first nine months of 2023 as compared to $23.3 million in the first nine months of 2022. Investment advisory income decreased $68,000, or 7.3%, primarily the result of a challenging investment market and economic conditions. These decreases were partially offset by a $218,000 gain on life insurance, the prior year period net realized loss on the sale of securities of $170,000 and a $118,000 increase in other income as the income from mortgage servicing rights increased.
For the third quarter of 2023, non-interest expense totaled $8.8 million, a decrease of $424,000, or 4.6%, over the comparable 2022 period. The decrease was primarily due to a decrease in salaries and benefits of $684,000, or 12.8%, as the number of employees decreased. Occupancy expense decreased $48,000, or 4.4%, due to a branch closure at the end of 2022. These decreases were partially offset by increased professional fees of $71,000 and an increase in other non-interest expenses of $164,000.
For the first nine months of 2023, non-interest expense totaled $27.3 million, a decrease of $522,000, or 1.9%, over the comparable 2022 period. The decrease was primarily due to a decrease in salaries and benefits of $1.5 million as the number of employees decreased when the Company made the difficult decision to layoff approximately 5% of its workforce in the first quarter of 2023, a decrease in occupancy expense of $179,000 due to the closure of our Monroe branch at the end of 2022 and a decrease in marketing fees of $80,000 due to decreased advertising. These decreases were partially offset by the growth in other non-interest expense of $713,000, or 17.0%, primarily due to a decrease in deferred loan commitments and inflationary pressures on our service contracts, an increase in FDIC deposit insurance assessments of $322,000, or 53.5%, and an increase in professional fees of $180,000.