ALLIANT ENERGY CORP

NOTE 5. COMMON EQUITY

Common Share Activity -A summary of Alliant Energy’s common stock activity was as follows:

At-the-Market Offering Programs - In March 2026, Alliant Energy fully utilized the remaining capacity under its $1.3 billion 2025 at-the-market offering program and Alliant Energy filed a new prospectus supplement and executed a related distribution agreement, under which it may sell up to $1 billion in aggregate of its common stock through 2029 through an at-the-market offering program that includes an equity forward sales component (the 2026 at-the-market offering program). Alliant Energy expects to use proceeds from the issuance of common stock for general corporate purposes.

Alliant Energy entered into a forward sale agreement under its 2026 at-the-market offering program with a counterparty who, for the three months ended March 31, 2026, borrowed and sold an aggregate of 362,000 shares of Alliant Energy common stock at an aggregate gross sales price of $26 million, including approximately $0.3 million in commissions to the counterparty payable by Alliant Energy when the forward sale agreements are settled. Alliant Energy has not yet received any proceeds from this program and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreement settles. Alliant Energy currently expects to settle the forward sale agreement prior to December 31, 2028 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of March 31, 2026, the weighted-average forward price, net of commissions, was $70.34 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of March 31, 2026, Alliant Energy could have settled all of its outstanding forward sale agreements under the 2026 at-the-market offering program with physical delivery of 362,000 shares of Alliant Energy common stock to the counterparty in exchange for cash of $25 million.

For the three months ended March 31, 2026, Alliant Energy entered into forward sale agreements under its 2025 at-the-market offering program with various counterparties who borrowed and sold an aggregate of 5,002,675 shares of Alliant Energy common stock at an aggregate gross sales price of $356 million, including approximately $3 million in commissions, to the counterparties payable by Alliant Energy when the forward sale agreements are settled. Alliant Energy has not yet received any proceeds from this program and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy currently expects to settle the forward sale agreements in 2026 and 2027 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of March 31, 2026, the weighted-average forward price, net of commissions, of all of the outstanding forward agreements under the 2025 at-the-market offering was $65.99 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of March 31, 2026, Alliant Energy could have settled all of its outstanding forward sale agreements under the 2025 at-the-market offering program with physical delivery of 19,598,207 shares of Alliant Energy common stock to the counterparties in exchange for cash of $1,293 million.

Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. For the quarter ended March 31, 2026,976,170 andno incremental shares were included in the calculation of diluted EPS related to the securities under the forward sale agreements for the 2025 and 2026 at-the-market offering programs, respectively.

Changes in Shareowners’ Equity -A summary of changes in shareowners’ equity was as follows (in millions):