ALLIANT ENERGY CORP

NOTE 11. INCOME TAXES

Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):

Income Tax Rates -The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. In 2024, Alliant Energy’s and IPL’s effective income tax rates were impacted by the pre-tax non-cash charge of $60 million for IPL’s Lansing Generating Station discussed in Note 2. In the fourth quarter of 2025, Alliant Energy, IPL and WPL retrospectively adopted the Financial Accounting Standards Board’s (FASB) accounting standard for improvements to income tax disclosures. Previously reported information for prior periods has been recast to conform with current period presentation.

Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

Carryforwards -At December 31, 2025, carryforwards and expiration dates were estimated as follows (in millions):

State Income Tax Apportionment - Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state income tax apportionment. Estimates of state income tax apportionment are supported by historical data and reasonable projections. Alliant Energy currently expects an increase in total state income tax apportionment primarily due to an increase in projected electric utility revenues driven by demand for energy from commercial and industrial customers, including demand from IPL’s and WPL’s executed electric service agreements with customers who expect to build data centers in their service territories. Alliant Energy parent company’s deferred tax assets were remeasured to reflect an increase in estimated total state income tax apportionment, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in 2025.

Uncertain Tax Positions -At December 31, 2025, 2024 and 2023, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2025, no material changes to unrecognized tax benefits are expected during the next 12 months.

Open tax years -Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

(a)The 2022 federal tax return is effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b)The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

Iowa Tax Reform -Pursuant to Iowa tax reform enacted in 2022, annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if the minimum receipt threshold is met. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 7.1% effective January 1, 2024.

Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured in 2023 based upon the new rate effective January 1, 2024, which resulted in a $74 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2023. In addition, Iowa tax reform made Iowa state income taxes fully deductible for the purpose of determining Iowa state income tax obligations beginning with the 2023 tax year. Alliant Energy reflected the deduction of the additional Iowa state income taxes in its 2023 Iowa state income tax return filed in 2024, which resulted in a $26 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2024. The reductions in tax-related regulatory assets are expected to provide cost benefits to IPL’s customers in the future.

Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2024, and the deduction of Iowa state income taxes included in Alliant Energy’s 2023 Iowa state income tax return filed in 2024, which resulted in charges of $10 million and $11 million recorded to income tax expense in Alliant Energy’s income statements and an increase in deferred income tax liabilities on Alliant Energy’s balance sheets in 2023 and 2024, respectively. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.