William Colgin

William Colgin is a partner at Holland & Hart in Jackson, Wyoming, who represents corporate taxpayers in complex federal tax controversies and tax litigation. His work includes high-stakes disputes involving international tax, transfer pricing, intellectual property, economic substance, and other contested federal tax issues. He litigates in the US Tax Court, federal district courts, state courts, and appellate courts. He also guides clients through Internal Revenue Service examinations, appeals, disclosure disputes, and coordinated multistate tax matters.

Colgin earned a J.D. from the University of Denver College of Law in 1992. He previously received an M.A. from the University of Wyoming in 1989 and a B.A. from the University of Wyoming in 1987. His academic background supports a practice centered on tax analysis, litigation strategy, and complex federal controversy work. The combination of legal and graduate-level study complements his experience evaluating disputed tax positions, building litigation records, and presenting matters before administrative bodies and courts.

Colgin began his tax litigation career as a trial attorney in the Tax Division of the US Department of Justice. He later practiced as a partner at Morgan Lewis before joining Holland & Hart. He now handles IRS examinations and appeals, tax litigation, anonymous disclosure disputes, multistate matters, and federal criminal and civil tax investigations involving the Justice Department and US Attorney’s Offices. His practice regularly requires coordinating factual, financial, regulatory, and litigation issues across multiple forums.

William Colgin is recognized for tax law and tax controversy work, including listings in Chambers USA and The Best Lawyers in America. He has held leadership roles in tax-law organizations, including service with the California Bar Taxation Section and American Bar Association Tax Section committees. His experience spans government enforcement, private practice, administrative proceedings, and courtroom litigation. That background allows him to advise corporate taxpayers through investigations, negotiations, appeals, and trials involving significant financial and operational consequences.

Law Office Affiliations

• Partner, Holland & Hart LLP
• Member, Wyoming State Bar
• Member, Colorado Bar Association
• Executive Committee, Taxation Section, Past Vice Chair, The State Bar of California
• Past Director, Tax Court Pro Se/Pro Bono Program, San Francisco, California
• Technology Subcommittee, Past Chair, American Bar Association, Tax Section
• Past Member, Advisory Board for the University of San Diego School of Law Procopio International Tax Institute

Licensed State

• Wyoming
• Colorado
• California

Education

• University of Denver College of Law
  Juris Doctor (JD)
• University of Wyoming
  Master of Arts (MA)
• University of Wyoming
  Bachelor of Arts (BA)

Awards & Badges