Exhibit 99.1 Vertex Announces Fourth Quarter and Full Year 2023 Financial Results KING OF PRUSSIA, PA – February 29, 2024: Vertex, Inc. (NASDAQ: VERX) (“Vertex” or the “Company”), a leading global provider of indirect tax solutions, today announced financial results for its fourth quarter and full year ended December 31, 2023. “The Vertex execution engine delivered exceptionally strong financial results in the fourth quarter,” stated David DeStefano, Vertex Chief Executive Officer. “Our year-over-year reven ...