ALLIANT ENERGY CORP

NOTE 6. DEBT

NOTE 6(a) Short-term Debt - In March 2026, Alliant Energy, IPL and WPL reallocated credit facility capacity amounts to $700 million for Alliant Energy at the parent company level, $300 million for IPL and $300 million for WPL, within the $1.3 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper and borrowings under the single credit facility classified as short-term debt was as follows (dollars in millions):

In March 2026, Alliant Energy entered into a $400 million variable rate (4.5% as of September 30, 2026) term loan credit agreement, which matures in March 2027 and is recorded in “Other short-term borrowings” on Alliant Energy’s balance sheet as of September 30, 2026. Alliant Energy’s term loan credit agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $100 million. The proceeds were used for general corporate purposes.

In October 2026, Alliant Energy, IPL and WPL reallocated credit facility amounts to $700 million for Alliant Energy at the parent company level, $250 million for IPL and $350 million for WPL, within the $1.3 billion total commitment.

NOTE 6(b) Long-term Debt - In January 2026, AEF retired its $300 million variable rate term loan. In March 2026, AEF retired its $200 million of 1.4% senior notes.

In August 2026, IPL issued $500 million of 5.1% senior debentures due 2031. The net proceeds from this issuance were used to reduce cash amounts received from its sale of accounts receivable program, reduce its outstanding commercial paper, including $50 million of commercial paper classified as long-term debt, and for general corporate purposes.

Convertible Senior Notes

2026 Notes - Alliant Energy’s $575 million of 3.875% convertible senior notes issued in March 2023 matured in March 2026. Alliant Energy settled its related conversion obligations to holders by paying the aggregate principal amount outstanding of $575 million in cash, and issuing 834,811 shares of Alliant Energy common stock for the excess of its conversion obligation over such principal amount, which was classified as a non-cash financing activity.

2028 Notes - In May 2025, Alliant Energy issued $575 million of 3.25% convertible senior notes (the 2028 Notes), which are senior unsecured obligations. As of September 30, 2026, the conditions allowing holders to convert their 2028 Notes were not met, and the 2028 Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of September 30, 2026, the net carrying amount was $571 million, with unamortized debt issuance costs of $4 million, and the estimated fair value (Level 2) was $573 million. For the three and nine months ended September 30, 2026, there wereno shares of Alliant Energy’s common stock related to the potential conversion of the 2028 Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the 2028 Notes.