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.

For the three months ended September 30, 2026, Alliant Energy did not enter into any forward sale agreements under its 2026 at-the-market offering program. 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 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 September 30, 2026, the weighted-average forward price, net of commissions, was $72.89 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 September 30, 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 6,912,857 shares of Alliant Energy common stock to the counterparties in exchange for cash of $504 million.

During the three months ended September 30, 2026, Alliant Energy did not settle any forward sale agreements under its 2025 at-the-market offering program. During the nine months ended September 30, 2026, Alliant Energy physically settled its obligations under various forward sale agreements entered into under its 2025 at-the-market offering program with the issuance and delivery of 929,759 shares of common stock at a weighted average forward sale price of $63.24 per share, net of commissions. Alliant Energy received net proceeds of $59 million, which were recorded in equity on Alliant Energy’s balance sheet. Alliant Energy used the net proceeds for general corporate purposes, which included repayment of commercial paper. Alliant Energy currently expects to settle the remainder of the 2025 at-the-market offering program 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 September 30, 2026, the weighted-average forward price, net of commissions, of all of the outstanding forward agreements under the 2025 at-the-market offering program was $66.01 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 September 30, 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 18,668,448 shares of Alliant Energy common stock to the counterparties in exchange for cash of $1,232 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 three and nine months ended September 30, 2026,1,135,656 and 1,284,411 incremental shares, respectively, related to the forward sale agreements under the 2025 at-the-market offering program were included in the calculation of diluted EPS. For the three and nine months ended September 30, 2026, zero and 15,652 incremental shares, respectively, related to the forward sale agreements under the 2026 at-the-market offering program were included in the calculation of diluted EPS.

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