Photo of Sean R. Gannon

Sean R. Gannon

Senior Counsel


B.A. Marketing, Michigan State University

J.D. Western Michigan University, Thomas M. Cooley School of Law

Co-Founder and Articles Editor of the Thomas M. Cooley Journal of Practical and Clinical Law (1996-1997), Recipient of the Moot Court Scholarship Award (1995), Member of the Philip C. Jessup International Law National Moot Court Competition Team (1997)

LL.M. - Taxation, University of Florida, Levin College of Law


Nominated for the Chief Counsel Attorney Excellence (Fred Goldberg, Jr.) Award (2010)

Bar Admissions


Court Admissions

U.S. District Court for the Northern District of Illinois

U.S. Tax Court


Michigan Tax Tribunal


Sean Gannon is a tax controversy and litigation attorney with a strong technical background and a detailed understanding of IRS procedural matters.  Sean’s practice focuses on representing clients in IRS examinations, appeals and litigation.  

Prior to joining Chamberlain Hrdlicka, Mr. Gannon served as a member of the management group of the Tax Controversy practice for a “Big Four” accounting firm, where he assisted clients with their IRS and state tax controversies, including advising on examination and collection matters, providing analysis of technical issues, addressing compliance issues arising from extraordinary filing requirements, and providing representation during IRS and state administrative appeals. Mr. Gannon routinely advised Fortune 500 companies, large FOF structures and closely held businesses and provided representation relative to a diverse spectrum of subject areas, including transfer pricing, intangible-asset valuation, research credits, debt-equity determinations, and loss deductions.

Mr. Gannon previously served as a Special Trial Attorney with the Office of Chief Counsel for the IRS, where he  was responsible for issuing written guidance for IRS revenue agents, appeals officers, and settlement officers on various substantive tax issues, as well as advancing and litigating some of the most important, sensitive, and complex tax cases for the Commissioner.

Professional Affiliations

  • American Bar Association