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This is a photo of Jeff Oldewening




Contact by email at [email protected]

t. 416-601-7778


Law School

University of Western Ontario

Bar Admission

Ontario, 2006

A recognized leader in corporate and cross-border tax law, Jeff helps clients navigate complex transactions and reorganizations

Jeff is a Partner in the Firm’s National Tax Group in Toronto with a practice focusing on domestic and cross-border mergers & acquisitions and reorganizations.  He develops success-driven tax planning structures.

Jeff is an experienced senior tax practitioner, renowned for developing innovative tax planning structures for multi-nationals and Canada’s leading financial institutions. He has extensive experience guiding clients, including a variety of pension plans, through complex domestic and cross-border M&A transactions, reorganizations and investments. He is one of the leading tax advisors in Canada in the area of corporate reorganizations and butterfly transactions. 

Jeff frequently acts for clients across a range of industry groups. Jeff teaches butterfly transactions at the Tax Law for Lawyers course and, for several years, lectured on capital gains stripping and divisive reorganizations at the In-Depth Tax Course for CPA Canada.  He is a member of the editorial board for the International Tax Planning journal, and a contributor to the Canadian Tax Journal.

Jeff has advised on the Canadian tax aspects of a variety of deals and reorganizations, including the following transactions:

  • UnitedHealth Group, in connection with its acquisition of Catamaran Corporation for approximately US$12.8 billion;
  • Burger King Worldwide, in connection with its acquisition of Tim Hortons Inc. for approximately US$12.5 billion, the U.S. tax inversion of Burger King under Restaurant Brands International Inc., the related financing, which involved a US$3 billion preferred equity investment from Berkshire Hathaway Inc., a secured US$7.25 billion credit facility and a private placement of US$2.25 billion of second lien secured notes, and an associated tender offer for Tim Hortons' outstanding US$1.2 billion of debt securities;
  • Vistra Energy, in connection with its acquisition of assets from Crius Energy Trust;
  • Baxter International Inc., in connection with its spin-off of Baxalta Incorporated;
  • GlaxoSmithKline, in connection with its joint venture with Pfizer to combine their consumer healthcare businesses; and
  • Chrysler Canada, in respect of its restructuring.


The Douglas J. Sherbaniuk Distinguished Writing Award in respect of the paper cited as Jeff Oldewening, Rachel A. Gold and Chris Sheridan, “Statutory Ratification” (2016) 64:1 Canadian Tax Journal 293-325.  The Canadian Tax Foundation confers this honour for the best writing undertaken for the Canadian Tax Foundation every year.