"He is exceptionally knowledgeable about tax and has a really deep knowledge of the IRS."
Chambers USA 2022


Gary Wilcox is a partner in Mayer Brown's Washington DC office and a co-leader of the Tax Controversy & Litigation team. Previously, Gary served as a co-leader of PricewaterhouseCoopers' (PwC) US tax controversy practice, and led the tax practice at another international law firm. He also served as the deputy chief counsel of the US Internal Revenue Service (IRS), where he was in charge of approximately 700 attorneys in the Office of Chief Counsel and had primary responsibility within the IRS for developing its positions on technical tax issues and the issuance of regulations and rulings.

Gary's practice focuses on tax controversies and tax planning. He represents multinational corporations in the audit and appeals phases of an IRS dispute as well as in litigation. Gary has particular experience with controversies arising from complex transactions, typically in a cross-border context, such as leveraged distributions and other repatriations, intercompany debt, worthless stock deductions, and cost sharing arrangements. He has litigated significant cases in U.S. Tax Court involving intercompany debt (ScottishPower) and consolidated return issues (Duquesne Light).

Gary also has many years of experience advising clients on structuring mergers, acquisitions and internal reorganizations, and now regularly advises on planning issues arising from the Tax Cuts and Jobs Act. He is a frequent lecturer on corporate tax issues, and is an author of the BNA Tax Management Portfolio entitled "Corporate Acquisitions- (A), (B), and (C) Reorganizations."

Gary is ranked by Chambers USA in the Tax – District of Columbia category in 2022. Chambers USA has said “Gary is very strong" and "He is exceptionally knowledgeable about tax and has a really deep knowledge of the IRS."

For many years Gary has been recognized as a leading tax controversy lawyer in the International Tax Review Controversy Leaders Guide and named among the World’s Leading Tax Advisors (Euromoney) and the “Best Tax Lawyers” in Washington DC by Washington Post Magazine, Gary is a former council director of the American Bar Association's Tax Section and a fellow of the American College of Tax Counsel.


New York University School of Law, LLM in Taxation

University of Oklahoma College of Law, JD, with highest honors

Texas Tech University, BBA, cum laude, accounting


  • District of Columbia
  • Pennsylvania