during the three months ended March 31, 2021 versus the three months ended March 31, 2020. The decrease in net interest margin was primarily the result of the decrease in interest earning assets.
Provision for Loan Losses. The provision for loan losses increased $8,000 for the three months ended March 31, 2021 to $8,000 from $0 for the three months ended March 31, 2020. The allowance for loan losses was $858,000, or 1.13% of total loans, at March 31, 2021, compared to $850,000, or 1.22% of total loans, at December 31, 2020, and $850,000, or 1.22%, of total loans, at March 31, 2020. Classified (substandard, doubtful and loss) loans decreased to $0 at March 31, 2021 from $559,000 at December 31, 2020 and $564,000 at March 31, 2020. There were no non-performing loans at March 31, 2021, December 31, 2020 or March 31, 2020. There were no charge-offs or recoveries for the three months ended March 31, 2021 or the three months ended March 31, 2020.
Noninterest Income. Noninterest income increased $52,000, or 23.6%, to $272,000 for the three months ended March 31, 2021 from $220,000 for the three months ended March 31, 2020. The increase was due to increases of $16,000 in service charges and other income and $37,000 in fees on loans sold.
Noninterest Expense. Noninterest expense decreased $65,000, or 9.9%, to $593,000 for the three months ended March 31, 2021 from $658,000 for the three months ended March 31, 2020. This decrease was primarily due to a decrease of $32,000, or 7.5%, in salaries and employee benefits. The decrease in salaries and employee benefits resulted primarily from an increase of $167,000 in deferred loan origination costs on higher portfolio loan volume period to period, offset in part by an increase of $133,000 in salary and related expenses. There were also decreases of $2,000, or 3.8%, in occupancy expense, $7,000, or 25.9%, in data processing expense, $12,000, or 24.0%, in accounting and consulting expense and $16,000, or 28.1%, in other expenses. These decreases were offset in part by an increase of $1,000, or 9.1%, in legal expense due to increased costs of operating as a public company, and increases of $2,000, or 13.3%, in FDIC deposit insurance premiums and OCC assessments and $1,000, or 5.0%, in insurance expense.
In future periods, if we make grants of awards under our equity incentive plan which was approved by our stockholders, we would expect our noninterest expense to increase due to increased compensation expenses.
Income Tax Expense. There was no income tax expense for the three months ended March 31, 2021 or the three months ended March 31, 2020, principally due to net operating loss tax carryforwards from prior years. The effective tax rate was 0.00% for the three months ended March 31, 2021 compared to 0.00% for the same quarter in 2020.
To provide financial assistance and liquidity to taxpayers during the COVID-19 pandemic, the CARES Act amended the federal income tax rules with regard to the usage of net operating losses (“NOLs”) for corporate taxpayers. The CARES Act allows for the carryback of losses arising in a taxable year beginning after December 31, 2017, and before January 1, 2021, to be carried back to each of the five taxable years preceding the taxable year of the loss. The CARES Act also temporarily repeals the 80% limitation for NOLs arising in tax years beginning after December 31, 2017 and beginning before January 1, 2021 and carried to another tax year These NOLs are now permitted to fully offset the loss corporation’s pre-2021 taxable income.
Liquidity and Capital Resources. Liquidity describes our ability to meet the financial obligations that arise in the ordinary course of business. Liquidity is primarily needed to meet the borrowing and deposit withdrawal requirements of our customers and to fund current and planned expenditures. Our primary sources of funds are deposits, principal and interest payments on loans and securities and proceeds from the sale of loans. We also have the ability to borrow from the FHLB. At March 31, 2021, we had $19.4 million outstanding in advances from the FHLB, and had the capacity to borrow approximately an additional $15.4 million from the FHLB and an additional $6.6 million on a line of credit with First National Bankers’ Bank, Baton Rouge, Louisiana at this date.
While maturities and scheduled amortization of loans and securities are predictable sources of funds, deposit flows and loan prepayments are greatly influenced by general interest rates, economic conditions, and competition. Our most liquid assets are cash and short-term investments including interest-bearing deposits in banks. The levels of these assets are dependent on our operating, financing, lending, and investing activities during any given period.