William F. J. Ardinger



William F. J. Ardinger is a shareholder and served for three decades as the head of the firm’s Tax Practice Group. Bill focuses his practice on federal and state tax matters, business transactions, financial and wealth planning, and public policy matters. His work includes structuring business transactions in a tax-efficient manner, planning multi-jurisdictional business structures, and managing federal and state tax controversies. Bill advises non-profit healthcare organizations on how to structure affiliations that will fortify operations against the impacts of dramatic federal and state regulatory changes. Bill has been a leader of New Hampshire’s initiative to become a modern and leading jurisdiction for laws governing trusts and regulated trust companies, including representing wealthy families seeking to charter private trust companies focused solely on family interests. With respect to public policy matters, Bill represents clients before the New Hampshire Legislature and Congress on state and federal legislative and regulatory initiatives involving tax, budget, and economic development policies.

Bill is recognized in The Best Lawyers in America for tax law, and he is recognized as one of the leading corporate/commercial/tax lawyers in New Hampshire by Chambers USA: America’s Leading Business Lawyers.

Prior to joining the Rath, Young, and Pignatelli in 1989, Bill practiced law with the Washington D.C. law firm of Patton Boggs, LLP, where he represented clients on complex business tax matters and public policy matters before the federal tax legislative process, including many aspects of the 1986 Tax Reform Act. Bill was elected to the New Hampshire House of Representatives in 1980 to represent his hometown of Cornish. While in the State Legislature, Bill served on the Ways and Means Committee.

Bill lives in Concord, New Hampshire with his wife, Kassandra Spanos Ardinger, and enjoys visiting his children and grandchildren in various places.

William F. J. Ardinger


Education and Bar Admissions


  • Harvard Law School, J.D., cum laude, 1985
  • University of New Hampshire, B.A., summa cum laude, Economics, 1982

Bar Admissions:

  • New Hampshire
  • District of Columbia Court of Appeals
  • U.S. Tax Court

Representative Matters

  • Representing a coalition to develop and lobby successfully for enactment of legislation to modernize New Hampshire’s statutes governing trust companies and trusts, which the Wall Street Journal described as “a bill that seeks to surpass most other states in innovative trust features”.
  • Representing a European-based multinational business with respect to the U.S. federal and state tax consequences of its U.S. enterprises and activities.
  • Representing the City of Nashua with respect to its acquisition of the formerly publicly-traded, private water utility that serves its residents and those of surrounding communities.
  • Representing a Fortune 100 company to successfully resolve an IRS audit challenge to a claim of tax credits for the sale of synthetic fuel under section 29 of the Internal Revenue Code; the final report proposed “no change” in the taxpayer’s position.
  • Representing “family offices” on business, tax and wealth management matters, including the formation of a “family fiduciary company” to serve as a long-term trustee for family wealth.
  • Representing a Fortune 100 company to challenge New Hampshire’s discriminatory and unconstitutional taxation of foreign dividends under the Foreign Commerce Clause of the United States Constitution.
  • Representing the administrator of New Hampshire’s UNIQUE college savings program to obtain the first favorable private letter ruling from the IRS for such a “Section 529” college savings plan.
  • Assisting the New Hampshire Legislature in creating the state Business Finance Authority to replace the Industrial Development Authority, and then representing the BFA to help it extend credit to hundreds of New Hampshire businesses that create and preserve thousands of jobs.
  • Assisting a Republican Governor with respect to the enactment of New Hampshire’s Business Enterprise Tax, an additive-method consumption-based tax.

Community Involvement

Community Involvement:

  • Member, Governor’ Office for Emergency Relief and Recovery’s Stakeholder Advisory Board, 2020-present
  • Member, Friends of Bridges House Board of Directors, 2017-present
  • Member, Commission to Study Public School Funding, 2020-2021
  • Member, Board of Trustees, University System of New Hampshire, 2008-2014
  • Member, Board of Trustees, Concord Community Music School, 1999-2005, Chairperson, 2004-2005

Professional Activities

  • Member, New Hampshire Board of Bar Examiners, 2008-2015
  • Member, New Hampshire Supreme Court Advisory Committee on Rules, 2005-2014


  • Bill Ardinger presented “State Tax Policy Update-Including State Tax Implications of Federal Tax Reform” at the 2017 COST North Atlantic Regional State Tax Seminar in Waltham, MA (June 22, 2017).
  • Bill Ardinger presents “Special Report–Tax Havens–The Coming Storm at Council on State Taxation’s North Atlantic Regional State Tax Seminar” in Hartford, Connecticut (December 10, 2015).
  • Bill Ardinger and Chris Sullivan present, “The Impact of Federal Legislative Developments on State and Local Taxes Affecting NH Business” at 31st Annual Tax Forum in Concord, NH (October 31, 2013).
  • Bill Ardinger, Chris Sullivan and Kathryn Michaelis, present, “2013 Massachusetts Tax Law Changes–Impact on NH Tech Industry”, NH High Tech Council (October 9, 2013).
  • Presentation, “State Taxation of Passthrough Entities: Key Issues and Current Developments,” COST North Atlantic Regional State Tax  Seminar, Waltham, MA (October 2, 2012).
  • Presentation, “Special Problems in the Division of Globally Earned Income,” Georgetown Law Advanced State & Local Tax Institute, Washington, DC (May 19, 2011).
  • Bill Ardinger, Kathryn Michaelis, “New Hampshire Challenges Massachusetts’ Use Tax Collection,” State Tax Notes, p. 425 (May 9, 2009).
  • Bill Ardinger, Kathryn Michaelis and Stan Arnold, “An Update on Vermont’s Shift to Combined Filing”, State Tax Notes, p. 502 (August 18, 2008).
  • Bill Ardinger, “Keep an Eye on New Hampshire–Comments on Massachusetts Question 1,” Commonwealth, p. 98 (Fall 2008).
  • Testimony to the Massachusetts Business Tax Study Commission, “New Hampshire’s Business Enterprise Tax,” (September 2007).
  • Kathryn Michaelis, Bill Ardinger and Stan Arnold, “Vermont Goes Unitary In 2006 and Beyond,” State Tax Notes, p. 59 (July 2, 2007).
  • Bill Ardinger and Michelle Arruda, “The Policy and Provisions of the Trust Modernization and Competitiveness Act of 2006,” New Hampshire Bar Journal, p. 6 (August 2006).
  • Testimony to the Pennsylvania Business Tax Reform Commission, “New Hampshire’s Business Enterprise Tax: Practical Experience with an ‘Entity Level’ Tax,” (November 2004).
  • Stan Arnold and Bill Ardinger, “Top Ten Reasons Why New Hampshire’s BET May Provide An Answer to State Tax Reform,” State Tax Notes, p. 583 (November 29, 2004).
  • Testimony to the Tennessee Tax Study Structure Commission, “New Hampshire’s Business Enterprise Tax: Practical Tax Reform in an Era of ‘Just Say No’,” (October 2003).

Awards and Recognitions