ALLIANT ENERGY CORP

NOTE 12. COMMITMENTS AND CONTINGENCIES

NOTE 12(a) Capital Purchase Commitments -Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including expansion of IPL’s gas generation and IPL’s and WPL’s expansion of energy storage. At September 30, 2026, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $318 million, $253 million and $65 million, respectively.

Tariff-Related Costs -In February 2026, the Supreme Court ruled that the International Emergency Economic Powers Act (IEEPA) does not provide the Executive Branch of the U.S. government with authority to impose tariffs, and, in March 2026, the Court of International Trade ordered Customs and Border Protection to refund certain IEEPA tariffs previously collected. Certain third-party suppliers engaged by IPL and WPL act as importers of record and may be eligible for refunds of tariffs previously paid. At September 30, 2026, Alliant Energy, IPL and WPL concluded that recovery of certain tariff costs was probable. As a result, tariff cost recoveries of $61 million at Alliant Energy, including $47 million at IPL and $14 million at WPL, were recorded as reductions of previously capitalized construction costs associated with energy storage facilities and classified as non-cash investing activities in the statements of cash flows. In October 2026, Alliant Energy received $61 million of cash proceeds related to these tariff cost recoveries, including $47 million at IPL and $14 million at WPL.

NOTE 12(b) Other Purchase Commitments -Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. Purchased power commitments primarily relate to minimum payments associated with electric generating capacity agreements. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2026, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but require payment when electricity is generated by the provider and amounts for future commitments to deliver power to electric customers that do not have current minimum thresholds but will be billed for requirements when power is provided, were as follows (in millions):

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2026.

NOTE 12(c) Guarantees and Indemnifications -

Whiting Petroleum Corporation (Whiting Petroleum) -In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum, an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, has guaranteed the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations.

Whiting Petroleum previously completed bankruptcy proceedings and business combinations, which substantially reduce the likelihood that Alliant Energy will be obligated to make any payments under these guarantees. As of September 30, 2026, the currently known partnership obligations for the abandonment obligations are estimated at $92 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy is not currently aware of, nor does it currently expect to incur in the future, any material liabilities related to these guarantees and therefore has not recognized any material liabilities related to these guarantees as of September 30, 2026 and December 31, 2025.

Non-utility Wind Farm in Oklahoma -In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term purchased power agreement (PPA). Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $27 million as of September 30, 2026 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of September 30, 2026 and December 31, 2025.

Transfers of Renewable Tax Credits - IPL and WPL have entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash. As of September 30, 2026, IPL and WPL provided indemnifications associated with $391 million and $310 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in the event of an adverse interpretation of tax law, including whether the related tax credits meet the qualification requirements. Alliant Energy, IPL and WPL believe the likelihood of having to make any material cash payments under these indemnifications is remote.

Electric Transmission Infrastructure - IPL and WPL have entered into agreements with their respective electric transmission service providers related to the construction of infrastructure necessary for the data centers that are expected to be built in IPL’s and WPL’s service territories by certain of their customers. If these construction projects were to be terminated prior to the infrastructure being placed in service by the electric transmission service providers, then IPL or WPL must reimburse their respective provider for the related costs incurred to-date. As of September 30, 2026, IPL’s and WPL’s related guarantees were approximately $199 million and $125 million, respectively. Alliant Energy, IPL and WPL are not aware of any material liabilities related to these guarantees that it is probable that they will be obligated to pay and therefore have not recognized any material liabilities related to these guarantees as of September 30, 2026 and December 31, 2025.

NOTE 12(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites -IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2026, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

Other Environmental Contingencies -In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Cross-State Air Pollution Rule, Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the Clean Air Act.

NOTE 12(e) Collective Bargaining Agreements - In May 2026, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired. A new agreement was reached in September 2026, which expires May 31, 2030.