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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 □ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FORM 10 - K For the Fiscal Year Ended December 31 , 2020 □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-13718 MDC PARTNERS INC . ( Exact Name of Registrant as Specified in Its Charter ) Canada ( State or Other Jurisdiction of Incorporation or Organization ) Title of Each Class Class A Subordinate Voting Shares , no par value 98-0364441 ( I.R.S. Employer Identification Number ) One World Trade Center , Floor 65 , New York , New York 10007 ( 646 ) 429-1800 ( Address , Including Zip Code , and Telephone Number , Including Area Code , of Registrant's Principal Executive Offices ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbols Name of Each Exchange on Which Registered NASDAQ MDCA 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 . Yes o No ý Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes o No ý 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 . Yes ý No o 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 ) . Yes ý No o 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 . Large accelerated filer o Accelerated filer ý Non - accelerated filer o Smaller reporting company > Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . o Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes □ No ý The aggregate market value of the shares of all classes of voting and non - voting common stock of the registrant held by non - affiliates as of June 30 , 2020 , the last business day of the Registrant's most recently completed second fiscal quarter , was approximately $ 120.0 million , computed upon the basis of the closing sales price $ 2.08 of the Class A subordinate voting shares on that date . As of February 25 , 2021 , there were 73,722,720 outstanding shares of Class A subordinate voting shares without par value , and 3,743 outstanding shares of Class B multiple voting shares without par value , of the registrant . DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant's Proxy Statement relating to the 2021 Annual General Meeting of Stockholders are incorporated by reference in Part III of this Annual Report on Form 10 - K where indicated .