decrease in accumulated other comprehensive loss, net of tax. Book value per common share was $30.42 at December 31, 2022, compared to $29.07 at September 30, 2022, and $30.75 at December 31, 2021.
The Bank is well capitalized under the minimum capital requirements established by the Federal Deposit Insurance Corporation (“FDIC”) with a total risk-based capital ratio of 13.7%, a Tier 1 leverage capital ratio of 11.3%, and a common equity Tier 1 (“CET1”) capital ratio of 12.5% at December 31, 2022.
The Company exceeded all regulatory capital requirements with a total risk-based capital ratio of 14.0%, a Tier 1 leverage capital ratio of 9.7%, and a CET1 ratio of 10.7% at December 31, 2022.
Credit Quality
The allowance for credit losses on loans (“ACLL”) at December 31, 2022, increased to $28.0 million, or 1.26% of gross loans receivable, excluding loans HFS, compared to $26.4 million, or 1.25% of gross loans receivable, excluding loans HFS at September 30, 2022, and $25.6 million, or 1.46% of gross loans receivable, excluding loans HFS, at December 31, 2021. The $1.6 million increase in the ACLL through the provision of credit losses was primarily due to higher risks from economic uncertainty, the increase in loans, and increased reserves on individually evaluated nonaccrual loans. The $2.4 million increase in the ACLL at December 31, 2022, from December 31, 2021, was primarily due to the growth in loans, partially offset by the one-time cumulative-effect adjustment of $2.9 million as of the CECL adoption date of January 1, 2022. The allowance for credit losses on unfunded loan commitments decreased $545,000 to $2.5 million at December 31, 2022, compared to $3.1 million at September 30, 2022, and increased $2.0 million from $499,000 at December 31, 2021.
Nonperforming loans increased $411,000 to $8.7 million at December 31, 2022, from $8.2 million at September 30, 2022, and increased $2.8 million from $5.8 million at December 31, 2021. The increase in nonperforming loans at December 31, 2022, compared to the linked quarter was primarily due to an increase in nonperforming indirect home improvement loans of $455,000 and compared to the same period last year was primarily due to an increase in nonperforming commercial business loans of $1.9 million, indirect home improvement loans of $525,000, one-to-four-family loans of $440,000, and marine loans of $211,000.
Loans classified as substandard increased $3.6 million to $20.2 million at December 31, 2022, compared to $16.6 million at September 30, 2022, and increased $2.1 from $18.1 million at December 31, 2021. The quarter over linked quarter increase in substandard loans was attributable to increases of $2.1 million in one-to-four-family loans and $1.9 million in commercial real estate loans, partially offset by a decrease of $806,000 in commercial and industrial loans. The year over year increase in substandard loans was primarily due to increases of $4.5 million in commercial real estate loans, $522,000 in indirect home improvement loans, and $450,000 in one-to-four-family loans, partially offset by a decrease of $3.3 million in commercial and industrial loans. There was one other real estate owned (“OREO”) property in the amount of $570,000 at December 31, 2022, one OREO in the amount of $145,000 at September 30, 2022, compared to none at December 31, 2021.
At December 31, 2022 and September 30, 2022, the Company had two commercial business loans totaling $3.7 million and $3.8 million, respectively, classified as troubled debt restructured (“TDRs”) loans, compared to none at December 31, 2021. These TDRs were nonaccrual loans at December 31, 2022 and 2021.
Operating Results
Net interest income increased $6.6 million, to $29.3 million for the three months ended December 31, 2022, from $22.7 million for the three months ended December 31, 2021. This comparable quarter over quarter increase was primarily the result of an improved mix of loans versus other interest-bearing assets and increased balances in