HUNTINGTON INGALLS INDUSTRIES INC

8. INCOME TAXES

The Company's earnings are primarily domestic, and its effective income tax rates on earnings from operations for the three months ended September 30, 2024 and 2023, were 9.8% and 21.7%, respectively. For the nine months ended September 30, 2024 and 2023, the Company's effective income tax rates on earnings from operations were 16.6% and 21.9%, respectively. The lower effective tax rate for the three months ended September 30, 2024, was primarily attributable to current and prior period research and development tax credits recorded in the current period. The lower effective tax rate for the nine months ended September 30, 2024, was primarily attributable to current and prior period research and development tax credits recorded in the current period and to a taxable gain associated with the sale of the Company’s interest in an unconsolidated ship repair and specialty fabrication joint venture recorded in 2023.

For each of thethree and nine months ended September 30, 2024, the Company’s effective tax rate differed from the federal statutory corporate income tax rate of 21% primarily due to research and development tax credits for the current and prior periods.

The Company's unrecognized tax benefits increased by $5 million and $9 million during thethree and nine months ended September 30, 2024, respectively. As of September 30, 2024, the estimated amounts of the Company's unrecognized tax benefits, excluding interest and penalties, were liabilities of $107 million. Assuming a sustainment of these tax positions, a reversal of $83 million of the accrued amounts would favorably affect the Company's effective federal income tax rate in future periods.

The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. For the three and nine months ended September 30, 2024, interest resulting from the unrecognized tax benefits noted above increased income tax expense by $1 million and $4 million, respectively.

Non-current state income taxes include deferred state income taxes, which reflect the change in deferred state tax assets and liabilities and the tax expense or benefit associated with changes in unrecognized state tax benefits in the relevant period. These amounts are recorded within operating income. Current period state income tax expense is charged to contract costs and included in cost of sales and service revenues in segment operating income.