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Mark S. Klein

Partner, Chairman of the Firm
  • New York
  • New Jersey
  • Florida
  • U.S. Supreme Court

State University College at Buffalo, B.S., Summa Cum Laude

University at Buffalo School of Law, J.D., Magna Cum Laude

Mark is Chairman of the Firm and concentrates his practice in New York State and New York City tax matters. He has more than 35 years of experience with federal, multistate, state and local taxation -- and may be best known for his public speaking on tax topics. Mark splits his time between the Firm's New York City and Buffalo offices.

Mark has represented numerous Fortune 500 companies in connection with corporate, withholding and sales tax audits as well as dozens of individuals who appear on the Forbes 400 list of wealthiest individuals in the United States. He has also been quoted in dozens of newspapers and periodicals, including The New York Times, The Wall Street Journal, Newsday, The Boston Globe and the Associated Press. Mark has appeared as a state tax expert on CNBC, CNN and other news outlets.

Mark taught courses in the Tax Certificate Program in the School of Management at the University of Buffalo on state taxation and tax practice and procedure. He is a member of The CPA Journal editorial review board and has written numerous books, articles and treatises on the subject of multistate taxation. Mark is the general editor of LexisNexis Tax Practice Insights: New York; the editor of New York Tax Highlights and the contributing editor of CCH's Annual Guidebook to New York Taxes. He is the co-author of the ABA Sales & Use Tax Desk Book, CCH's New York Residency and Allocation Audit Handbook; New York Sales and Use Tax Answer Book, the New York State Bar Association's Contesting New York State Tax Assessments, 4th Edition; and CCH's New York Sales and Use Tax. Mark is also a contributor to numerous professional and industry-focused publications.


  • Listed, Best Lawyers in America, "Lawyer of the Year" (Litigation and Controversy - Tax), 2021
  • Listed, New York Metro Super Lawyers, 2019 - 2021 (Tax)
  • Listed, Best Lawyers in America (Tax Law, Litigation and Controversy -Tax) 1995 - 2022
  • Listed, Upstate New York Super Lawyers, (Tax) 2007 - 2021
  • Listed, Buffalo Business First/Buffalo Law Journal’s Legal Elite of Western New York Legal Leader, 2018 - 2020

  • Who's Who in American Law
  • Martindale-Hubbell, 1998-2020 – highest possible peer review rating in legal ability & ethical standards for 22 years

In the News

Mark is frequently interviewed and quoted by media outlets throughout the United States.

Press Releases


Blog Posts

Presentations & Events

Professional Associations

  • New York State Tax Appeals Tribunal Advisory Committee
  • Executive Committee of ACE Accounting Society
  • Editorial review board, New York State Society of CPAs' CPA Journal
  • Former chair, Bar Association of Erie County Cooperation with the Accounting Profession Committee
  • American Bar Association Tax Committee
  • New York State Bar Association Tax Committee
  • Former chair, Bar Association of Erie County Tax Committee