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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 Commission file number 1-03560 G GLATFELTER 4350 Congress Street , Suite 600 Charlotte , North Carolina 28209 ( Address of principal executive offices ) ( 704 ) 885-2555 ( Registrant's telephone number , including area code ) Exact name of registrant as specified in its charter Glatfelter Corporation IRS Employer Identification No. 23-0628360 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) . GLT State or other jurisdiction of incorporation or organization Pennsylvania Title of Each Class share Common Stock , par value $ .01 per 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 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 No . No . Name of Each Exchange on which registered New York Stock Exchange 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 , or a small reporting company . See the definitions of " large accelerated filer " , " accelerated filer " and " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Accelerated filer Non - accelerated filer Small reporting company Emerging Growth Company 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 Exchange Act ) . Yes No . Based on the closing price as of June 30 , 2020 , the aggregate market value of the Common Stock of the Registrant held by non - affiliates was $ 691.3 million . 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 . Common Stock outstanding on February 18 , 2021 totaled 44,367,836 shares . DOCUMENTS INCORPORATED BY REFERENCE Portions of the definitive Proxy Statement to be delivered to shareholders in connection with the Annual Meeting of Shareholders to be held on May 6 , 2021 are incorporated by reference into Part III .