SCHEDULE 13G/A 0001104659-21-021934 0001818517 XXXXXXXX LIVE 6 Class A Common Stock, $0.001 par value per share 06/30/2025 0001806837 Vertex, Inc. 92538J106 2301 Renaissance Boulevard King of Prussia PA 19406 Rule 13d-1(d) Amanda Radcliffe a X1 33188884.22 84210.00 33188884.22 84210.00 33273094.22 N 20.9 IN The amount in Row 9 includes (i) 59,182 shares of Class A Common Stock held of record by Amanda Radcliffe, (ii) 838,000 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by Ms. Radcliffe, (iii) 32,291,702.223 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held by trusts of which Ms. Radcliffe is the trustee and (iv) 84,210 shares of Class A Common Stock jointly held by Amanda Radcliffe and Conrad Radcliffe. Stefanie Thompson a X1 32986261.58 0.00 32986261.58 0.00 32986261.58 N 20.7 IN The amount in Row 9 includes (i) 51,357 shares of Class A Common Stock held of record by Stefanie Thompson, (ii) 838,000 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by Ms. Thompson and (iii) 32,096,904.588 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held by trusts of which Ms. Thompson is the trustee. Jeffrey Westphal a X1 1521822.23 0.00 1521822.23 0.00 1521822.23 N 1.0 IN The amount in Row 9 includes (i) 7,895 shares of Class A Common Stock held of record by Jeffrey Westphal, (ii) 388,000 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by Mr. Westphal and (iii) 1,125,927.237 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held by the 2009 Jeffrey R. Westphal Generation Skipping Trust, of which Mr. Westphal is the trustee. Christopher Thompson a X1 5629.04 0.00 5629.04 0.00 5629.04 N 0.004 IN The amount in Row 9 includes 5,629.046 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by Christopher Thompson. Benjamin Schmerin a X1 4221.78 0.00 4221.78 0.00 4221.78 N 0.003 IN The amount in Row 9 includes (i) 2,500 shares of Class A Common Stock held of record by Benjamin Schmerin and (ii) 1,721.784 shares of Class A Common Sock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by Benjamin Schmerin. Conrad Radcliffe a X1 0.00 2731647.37 0.00 2731647.37 2731647.37 N 1.7 IN The amount in Row 9 includes (i) 2,647,437.377 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Third Party Funded Special Needs Trust for Callum W. Radcliffe u/a of Amanda W. Radcliffe dated May 15, 2015, of which Conrad Radcliffe, Kailey Radcliffe and Antoinette Capik are the trustees and (ii) 84,210 shares of Class A Common Stock jointly held by Amanda Radcliffe and Conrad Radcliffe. Kailey Radcliffe a X1 2647437.37 2647437.37 2647437.37 2647437.37 5294874.75 N 3.3 IN The amount in Row 9 includes (i) 2,647,437.377 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Third Party Funded Special Needs Trust for Callum W. Radcliffe u/a of Amanda W. Radcliffe dated May 15, 2015, of which Conrad Radcliffe, Kailey Radcliffe and Antoinette Capik are the trustees and (ii) 2,647,437.377 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Kailey Radcliffe u/a of Amanda W. Radcliffe dated 10/05/2001, of which Kailey Radcliffe is the trustee. Antoinette Capik a X1 2647437.37 2647437.37 2647437.37 2647437.37 5294874.75 N 3.3 IN The amount in Row 9 includes (i) 2,647,437.377 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Third Party Funded Special Needs Trust for Callum W. Radcliffe u/a of Amanda W. Radcliffe dated May 15, 2015, of which Conrad Radcliffe, Kailey Radcliffe and Antoinette Capik are the trustees and (ii) 2,647,437.377 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Antoinette R. Radcliffe u/a of Amanda W. Radcliffe dated 10/05/2001, of which Antoinette R. Capik is the trustee. Anne Marie Westphal a X1 0.00 173074.00 0.00 173074.00 173074.00 N 0.1 IN The amount in Row 9 represents (i) 173,073.706 shares of Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Anne Marie Westphal u/a of Jeffrey R. Westphal dated 10/05/2001, of which Anne Marie Westphal is a trustee, and (ii) 0.294 shares of Class A Common Stock held of record by the 2020 Irrevocable Trust for Benefit of Nicholas A. Shuhan, of which Anne Marie Westphal's spouse is a trustee. Kyle Westphal a X1 0.00 1211100.00 0.00 1211100.00 1211100.00 N 0.8 IN The amount in Row 9 represents 1,211,100 shares of Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Kyle R. Westphal u/a of Jeffrey R. Westphal dated 10/05/2001, of which Kyle Westphal is a trustee. Jacob Westphal a X1 0.00 745706.00 0.00 745706.00 745706.00 N 0.5 IN The amount in Row 9 represents 745,706 shares of Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Jacob J. Westphal u/a of Jeffrey R. Westphal dated 10/05/2001, of which Jacob Westphal is a trustee. Melanie DeStefano a X1 1941750.00 0.00 1941750.00 0.00 1941750.00 N 1.2 IN The amount in Row 9 represents (i) 300,000 Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Melanie H. Lucas u/a of Stefanie W. Lucas dated 10/05/2001, of which Melanie DeStefano is the trustee and (ii) 1,641,750 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Melanie H. Lucas u/a of Stefanie W. Lucas dated 10/05/2001. Samantha Lucas a X1 1969895.22 0.00 1969895.22 0.00 1969895.22 N 1.2 IN The amount in Row 9 represents 1,969,895.229 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Samantha W. Lucas u/a of Stefanie W. Lucas dated 10/05/2001, of which Samantha Lucas is the trustee. Mackenzie Lucas a X1 1941750.00 0.00 1941750.00 0.00 1941750.00 N 1.2 IN The amount in Row 9 represents (i) 600,000 shares of Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Mackenzie S. Lucas u/a of Stefanie W. Lucas dated 10/05/2001, of which Mackenzie Lucas is the trustee and (ii) 1,341,750 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Mackenzie S. Lucas u/a of Stefanie W. Lucas dated 10/05/2001. Andrea Schmerin a X1 1983967.84 0.00 1983967.84 0.00 1983967.84 N 1.2 IN The amount in Row 9 represents (i) 400,000 shares of Class A Common Stock held of record by the Item Second Irrevocable Trust FBO Andrea P. Lucas u/a of Stefanie W. Lucas dated 10/05/2001, of which Andrea Schmerin is the trustee and (ii) 1,583,967.84 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the Item Second Irrevocable Trust FBO Andrea P. Lucas u/a of Stefanie W. Lucas dated 10/05/2001. Constance Thompson a X1 112580.91 0.00 112580.91 0.00 112580.91 N 0.1 IN The amount in Row 9 represents (i) 22,500 shares of Class A Common Stock held of record by the 2020 Irrevocable Trust for Benefit of Constance A. Thompson, of which Constance Thompson is the trustee and (ii) 90,080.918 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock held of record by the 2020 Irrevocable Trust for Benefit of Constance A. Thompson. Vertex, Inc. 2301 Renaissance Boulevard, King of Prussia, PA, 19406 Each of the following is hereinafter individually referred to as a "Reporting Person" and collectively as the "Reporting Persons." This statement is filed on behalf of: Amanda Radcliffe; Stefanie Thompson; Jeffrey Westphal; Christopher Thompson; Benjamin Schmerin; Conrad Radcliffe; Kailey Radcliffe; Antoinette Capik; Anne Marie Westphal; Kyle Westphal; Jacob Westphal; Melanie DeStefano; Samantha Lucas; Mackenzie Lucas; Andrea Schmerin; and Constance Thompson. The business address for each of the Reporting Persons is c/o Vertex, Inc., 2301 Renaissance Boulevard, King of Prussia, PA 19406. Each of the Reporting Persons is a citizen of the United States. Y The information contained on the cover pages to this Schedule 13G is incorporated by reference into this Item 4. The ownership information presented below represents beneficial ownership of Class A Common Stock of the Issuer as of June 30, 2025, based upon 77,318,571 shares of Class A Common Stock outstanding as of August 1, 2025, and assumes the conversion of an aggregate 82,155,641 shares of Class B Common Stock, par value $0.001 per share of the Issuer (the "Class B Common Stock"), held by the Reporting Persons on a one-for-one basis. Each of the Reporting Persons is a party to that certain Third Amended and Restated Stockholders' Agreement, dated as of July 28, 2020, by and among the Issuer and the Reporting Persons and associated trusts described above (the "Stockholders Agreement"). See Item 11 of each of the cover pages hereto. See Item 5 of each of the cover pages hereto. See Item 6 of each of the cover pages hereto. See Item 7 of each of the cover pages hereto. See Item 8 of each of the cover pages hereto. Y Y Y N By virtue of the Stockholders Agreement and the obligations and rights thereunder, the Reporting Persons acknowledge and agree that they are acting as a "group" with the other Stockholders within the meaning of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). Based in part on information provided by the Issuer, as of the date hereof, such a "group" would be deemed to beneficially own an aggregate of 85,751,483 shares of Class A Common Stock, or 53.8% of the Class A Common Stock of the Issuer calculated pursuant to Rule 13d-3 of the Exchange Act. Each Reporting Person expressly disclaims beneficial ownership over any shares of Class A Common Stock that they may be deemed to beneficially own solely by reason of the Stockholder Agreement. Y Y 99. Joint Filing Agreement (previously filed). Amanda Radcliffe /s/ Amanda Radcliffe 08/13/2025 Stefanie Thompson /s/ Stefanie Thompson 08/13/2025 Jeffrey Westphal /s/ Jeffrey Westphal 08/13/2025 Christopher Thompson /s/ Christopher Thompson 08/13/2025 Benjamin Schmerin /s/ Benjamin Schmerin 08/13/2025 Conrad Radcliffe /s/ Conrad Radcliffe 08/13/2025 Kailey Radcliffe /s/ Kailey Radcliffe 08/13/2025 Antoinette Capik /s/ Antoinette Capik 08/13/2025 Anne Marie Westphal /s/ Anne Marie Westphal 08/13/2025 Kyle Westphal /s/ Kyle Westphal 08/13/2025 Jacob Westphal /s/ Jacob Westphal 08/13/2025 Melanie DeStefano /s/ Melanie DeStefano 08/13/2025 Samantha Lucas /s/ Samantha Lucas 08/13/2025 Mackenzie Lucas /s/ Mackenzie Lucas 08/13/2025 Andrea Schmerin /s/ Andrea Schmerin 08/13/2025 Constance Thompson /s/ Constance Thompson 08/13/2025