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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C.20549 FORM 20 - F ( Mark One ) ☐ Registration statement pursuant to Section 12 ( b ) or ( g ) of the Securities Exchange Act of 1934 OR ☑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 OR Shell company report pursuant to section 13 or 15 ( d ) of the Securities Exchange Act of 1934 . Commission File Number : 333-08704 ICON PUBLIC LIMITED COMPANY ( Exact name of Registrant as Specified in its Charter ) ICON PLC ( Translation of Registrant's name into English ) Ireland ( Jurisdiction of Incorporation or Organization ) South County Business Park , Leopardstown , Dublin 18 , Ireland ( Address of principal executive offices ) Brendan Brennan , Chief Financial Officer South County Business Park , Leopardstown , Dublin 18 , Ireland . Brendan.Brennan@iconplc.com + 353-1-291-2000 ( Name , telephone number , email and / or facsimile number and address of Company contact person ) Securities registered or to be registered pursuant to Section 12 ( b ) of the Act : Title of each class ORDINARY SHARES , PAR VALUE € 0.06 EACH ICLR Name of exchange on which registered NASDAQ Global Select Market Securities registered or to be registered pursuant to section 12 ( g ) of the Act : Title of each class NONE Securities for which there is a reporting obligation pursuant to Section 15 ( d ) of the Act : NONE ( Title of class ) Indicate the number of outstanding shares of each of the issuer's classes of capital or common stock as of the close of the period covered by the annual report : 52,788,093 Ordinary Shares . Indicate by check mark if the registrant is a well - known seasoned issuer , as determined in Rule 405 of the Securities Act . Yes ☑ No ☐ If this report is an annual or transition report , indicate by check mark if the registrant is not required to file reports pursuant to section 13 or 15 ( d ) of the Securities Exchange Act of 1934. 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 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 and posted on its corporate Web site , if any , every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S - T during the preceding 12 months : Yes ☑ No ☐ Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , or a non- accelerated filer . Large accelerated filer ☑ Emerging growth company ☐ Accelerated filer Non - accelerated filer If an emerging growth company that prepares its financial statements in accordance with U.S. GAAP , 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 which basis of accounting the registrant has used to prepare the financial statements included in this filing : U.S. GAAP ☑ International Financial Reporting Standards as issued by the International Accounting Standards Board Other If " Other " has been checked in response to the previous question , indicate by check mark which financial statement item the registrant has elected to follow . Item 17 Item 18 If this is an annual report , indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) Yes ☐ No ☑