Annual report
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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Alliant Energy ™ Name of Registrant . State of Incorporation . Address of Principal Executive Offices . Telephone Number , Commission File Number , IRS Employer Identification Number ALLIANT ENERGY CORPORATION ( a Wisconsin Corporation ) 4902 N. Biltmore Lane Madison , Wisconsin 53718 Telephone ( 608 ) 458-3311 Commission File Number - 1-9894 IRS Employer Identification Number - 39-1380265 INTERSTATE POWER & LIGHT COMPANY ( an lowa corporation ) Alliant Energy Tower Cedar Rapids , lowa 52401 Telephone ( 319 ) 786-4411 Commission File Number - 1-4117 IRS Employer Identification Number - 42-0331370 WISCONSIN POWER & LIGHT COMPANY ( a Wisconsin corporation ) 4902 N. Biltmore Lane Madison , Wisconsin 53718 Telephone ( 608 ) 458-3311 Commission File Number - 0-337 IRS Employer Identification Number - 39-0714890 This combined Form 10 - K is separately filed by Alliant Energy Corporation , Interstate Power and Light Company and Wisconsin Power and Light Company . Information contained in the Form 10 - K relating to Interstate Power and Light Company and Wisconsin Power and Light Company is filed by each such registrant on its own behalf . Each of Interstate Power and Light Company and Wisconsin Power and Light Company makes no representation as to information relating to registrants other than itself . Securities registered pursuant to Section 12 ( b ) of the Act : Alliant Energy Corporation , Common Stock , $ 0.01 Par Value , Trading Symbol LNT , Nasdaq Global Select Market Interstate Power and Light Company , 5.100 % Series D Cumulative Perpetual Preferred Stock , $ 0.01 Par Value , Trading Symbol IPLDP , Nasdaq Global Select Market Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Alliant Energy Corporation - Yes > No Interstate Power and Light Company - Yes > No Wisconsin Power and Light Company - Yes > No Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act .