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Margaret Derus is of counsel in Reinhart’s Tax, Litigation and Tax-Exempt Organizations practices, where she draws on her considerable experience to handle complex issues. She represents mid-sized to large clients including manufacturers, utilities, telecommunications companies, airlines, commercial businesses and health care and housing providers. Her practice includes tax planning and tax litigation related to multistate income/franchise tax, sales/use tax, property tax and selected federal tax matters.

Before joining Reinhart, Margaret was second in command of the Wisconsin Department of Revenue (DOR) where she formulated and developed tax policy and legislation. She is also a Certified Public Accountant (CPA) and formerly worked at a national accounting firm. Collectively, her legal experience, DOR experience and CPA provide Margaret a unique perspective and holistic understanding of her clients’ issues, and she offers strategic solutions that consider both business and legal implications.

Margaret lends her historical knowledge of previous negotiations to young attorneys, offering helpful insight while strengthening the team and the community. She frequently speaks to business and industry audiences at local and national events on a variety of taxation issues. She was a faculty fellow at the University of Wisconsin Deloitte & Touche Center for Multistate Taxation and a guest lecturer at the University of Wisconsin-Milwaukee Masters of Science – Advanced State and Local Taxation Program.

In her free time, she loves traveling (especially in Europe), participating in a book club and spending time with her many nieces and nephews.


  • J.D., cum laude, University of Wisconsin Law School
  • B.A. in Accounting, summa cum laude, University of Wisconsin-Green Bay

Bar Admissions


Court Admissions

  • U.S. District Court, Eastern District of Wisconsin
  • U.S. Court of Appeals
  • U.S. Tax Court


  • Represented several manufacturers, airlines and telecommunications companies to challenge their property tax valuation and assessments, achieving substantial tax reductions
  • Defended her clients’ multistate apportionment factors for income/franchise tax purposes, providing substantial tax savings and future tax benefits
  • Defended multistate business clients challenging the imposition of tax on various types of transactions and nexus determinations for sales/use tax and income/franchise tax in various states
  • Develops entity, locational and transactional structuring to take advantage of differences in state tax laws
  • Challenged property valuation and exemption issues for manufacturing clients
  • Obtains significantly reduced property tax assessments for numerous commercial property owners
  • Assists health care, long-term care and housing providers and other nonprofit organizations in obtaining or retaining tax exemptions
  • Spearheaded a law change to reverse a Wisconsin Supreme Court decision that would have adversely affected many of the firm’s health care and housing provider clients

Honors & Affiliations


  • Best Lawyers in America (Tax Law; Litigation & Controversy-Tax)
  • Awarded Lawyer of the Year, Milwaukee Litigation and Tax Controversy by Best Lawyers in America (2016 and 2019)
  • Selected for inclusion in Wisconsin Super Lawyers
  • Wisconsin Top Rated Lawyer Martindale-Hubbell AV® Preeminent™ Peer Review Rated
  • State Bar of Wisconsin
  • Governor's Telecommunications Tax Study Committee
  • The Federation of Tax Administrators Motor Fuel Tax Committee on Uniform Legislation (former chair)
  • State and Local Tax, Inc. President; Board of Directors)
  • Wisconsin State Bar Tax Section (former Board of Directors)
  • Wisconsin Department of Revenue (Advisory Committee to the Secretary)
  • Wisconsin Manufacturers and Commerce (Tax Advisory Committee)

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