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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K ( Mark One ) 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_ Commission file number 1-39686 ( Apartment Income REIT Corp. ) Commission file number 0-24497 ( AIMCO Properties , L.P. ) APARTMENT INCOME REIT CORP . AIMCO PROPERTIES , L.P. ( Exact name of registrant as specified in its charter ) Maryland ( Apartment Income REIT Corp. ) Delaware ( AIMCO Properties , L.P. ) ( State or other jurisdiction of incorporation or organization ) 4582 South Ulster Street , Suite 1700 Denver , Colorado ( Address of principal executive offices ) Registrant's telephone number , including area code ( 303 ) 757-8101 Securities registered pursuant to Section 12 ( b ) of the Act : Title of Each Class Class A Common Stock ( Apartment Income REIT Corp. ) Trading Symbol ( s ) AIRC Securities registered pursuant to Section 12 ( g ) of the Act : None ( Apartment Income REIT Corp. ) Partnership Common Units ( AIMCO Properties , L.P. ) ( title of each class ) 84-1299717 84-1275621 ( I.R.S. Employer Identification No. ) 80237 ( Zip Code ) Name of Each Exchange on Which Registered New York Stock Exchange Indicate by check mark if the registrant is a well - known seasoned issuer , as defined by Rule 405 of the Securities Act . Apartment Income REIT Corp .: 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 . Apartment Income REIT Corp .: Yes No AIMCO Properties , L.P .: Yes No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Apartment Income REIT Corp .: Yes No AIMCO Properties , L.P .: Yes > No □ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Apartment Income REIT Corp .: Yes No AIMCO Properties , L.P .: Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . AIMCO Properties , L.P .: Yes No