The cost of deposits in the fourth quarter of 2020 was 0.16%, a decrease of 74 basis points from the fourth quarter of 2019 and a decrease of 3 basis points from the third quarter of 2020. The cost of interest bearing deposits decreased 111 basis points to 0.25% from the fourth quarter of 2019, and decreased 3 basis points from the third quarter of 2020.
The provision for credit losses was $481,000 in the fourth quarter of 2020 compared to $787,000 in the fourth quarter of 2019 and $28,000 in the third quarter of 2020. The fourth quarter of 2020 provision for credit losses included a $225,000 provision for loan losses and a $257,000 provision for unfunded commitments. The higher provision for unfunded commitments in the fourth quarter of 2020 was driven by an increase in the level of unfunded commitments.
Noninterest income totaled $3.0 million in the fourth quarter of 2020 compared to $2.7 million in the fourth quarter of 2019 and $2.5 million in the third quarter of 2020. Service charge income in the fourth quarter of 2020 totaled $1.3 million, an increase of $343,000 compared to the fourth quarter of 2019, and an increase of $124,000 from the third quarter of 2020. The increase in service charge income was primarily due to growth in our payments and fintech businesses along with solid growth in our core treasury management business. SBA income totaled $1.0 million, an increase from $893,000 in the third quarter of 2020, primarily from higher SBA origination volume.
Noninterest expense totaled $13.2 million in the fourth quarter of 2020, compared to $13.4 million in the fourth quarter of 2019 and $13.7 million in the third quarter of 2020. The $413,000 linked quarter decrease in salaries and benefits was primarily driven by an increase in loan production salary cost deferrals due to higher loan originations during the fourth quarter and a decrease in incentive compensation. In addition, other noninterest expense decreased in the fourth quarter of 2020 primarily from the recovery of $290,000 of the $470,000 in losses on customer accounts incurred during the third quarter of 2020.
The 2020 effective tax rate from continuing operations was 17.0% compared to 21.3% for the full year of 2019, and was impacted by lower pretax earnings as well as increased non-taxable securities income from municipal bonds.
Balance Sheet
Total loans held for investment were $2.25 billion at December 31, 2020, an increase of $375.5 million, or 20.0%, from December 31, 2019 and an increase of $61.0 million, or 11% annualized, from September 30, 2020. PPP loans totaled $192.2 million at December 31, 2020, a decrease of $40.0 million compared to September 30, 2020, due to the forgiveness of PPP loans during the fourth quarter. In addition to the strong funded loan growth across most of our lines of business, total unfunded commitments increased $50.0 million, on a linked quarter basis, primarily due to strong growth in our commercial real estate business.
The allowance for credit losses was 1.55% of total loans held for investment at December 31, 2020, compared to 1.59% at September 30, 2020. Excluding the impact of PPP loans, the allowance for credit losses at December 31, 2020 was 1.70% compared to 1.78% at September 30, 2020. Annualized net charge-offs were 0.05% for the fourth quarter of 2020 and 0.11% for the full year 2020. Non-performing assets totaled $4.9 million, or 0.13% of total assets, as of December 31, 2020, compared to $6.0 million, or 0.20% of total assets, as of September 30, 2020.
Total average deposits were $2.87 billion for the fourth quarter of 2020, an increase of $727.8 million, or 33.9%, from the fourth quarter of 2019 and an increase of $402.2 million, or 65.1% annualized, from the third quarter of 2020. In addition to typical seasonal increases in fourth quarter deposits, we continued to see strong growth in core deposits across most of our lines of business. Noninterest bearing deposits were 34.0% of total average deposits in the fourth quarter of 2020, compared to 33.5% in the fourth quarter of 2019 and 34.6% in the third quarter of 2020.
Tangible common equity to tangible assets decreased to 8.9% at December 31, 2020, compared to 11.0% September 30, 2020, due to the impact from the fourth quarter growth in deposits and its corresponding increase on the size of the year-end balance. Cash and cash equivalents were $653.4 million and total assets were $3.62 billion at December 31, 2020 compared to cash and cash equivalents of $114.0 million and total assets of $2.92 billion at September 30, 2020.