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( 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 ☐ UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K 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 001-35238 HORIZON THERAPEUTICS PUBLIC LIMITED COMPANY ( Exact name of Registrant as specified in its charter ) Ireland ( State or other jurisdiction of incorporation or organization ) Connaught House , 1st Floor 1 Burlington Road , Dublin 4 , D04 C5Y6 , Ireland ( Address of principal executive offices ) Title of Each Class Ordinary shares , nominal value $ 0.0001 per share Large accelerated filer Non - accelerated filer Not Applicable ( I.R.S. Employer Identification No. ) Trading Symbol HZNP Not Applicable ( Zip Code ) 011 353 1 772 2100 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Securities registered pursuant to Section 12 ( g ) of the Act : None Name of Each Exchange on Which Registered The Nasdaq Global Select Market No □ . Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes 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 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 . 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 during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . 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 . Accelerated filer Smaller reporting company 0 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 . 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 by Rule 12b - 2 of the Exchange Act ) . Yes No The aggregate market value of the registrant's voting ordinary shares held by non - affiliates of the registrant , based upon the $ 55.58 per share closing sale price of the registrant's ordinary shares on June 30 , 2020 ( the last business day of the registrant's most recently completed second quarter ) , was approximately $ 11.0 billion . Solely for purposes of this calculation , the registrant's directors and executive officers and holders of 10 % or more of the registrant's outstanding ordinary shares have been assumed to be affiliates and an aggregate of 2,590,708 ordinary shares held by such persons on June 30 , 2020 are not included in this calculation . As of February 17 , 2021 , the registrant had outstanding 224,047,600 ordinary shares . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive Proxy Statement for the registrant's 2021 Annual General Meeting of Shareholders are incorporated by reference into Part III of this Annual Report on Form 10 - K .