Jonathan Mariner



Founder and President

Jonathan Mariner

Jonathan Mariner is a private investor, entrepreneur, and independent board member with more than two decades of experience working in major league sports. He’s currently the founder and president of TaxDay, LLC, a private software firm that helps users track their multi-state travel for tax purposes.

Jonathan retired from Major League Baseball, Office of the Commissioner in 2016, having previously served as Executive VP and CFO, as well as Chief Investment Officer. His career in professional sports started in 1992, with a nine-year stint as Executive Vice President and CFO of the Florida Marlins Baseball Club. Jonathan concurrently served as Vice President and CFO of the Florida Panthers Hockey Club for the team’s initial startup and inaugural seasons, and as Vice President and CFO for Pro Player Stadium.

Jonathan currently serves on the Boards of Directors of Rocket Mortgage as the Chair of the Audit Committee and a member of the Compensation Committee; Tyson Foods, Inc, as Chair of the Audit Committee; and Five9, Inc. Jonathan also serves on the Boards of Directors of the following private companies: Delaware North; OneStream, Inc, Little League International (Audit Committee, Chair; Investment Committee, Co-chair), and Overtime Sports, Inc.

Jonathan graduated from the University of Virginia with a B.A. in accounting and received his M.B.A. from Harvard Business School.