About Ian Therrien

Ian Therrien handles the tax side of business deals and restructurings: financings, corporate reorganizations, and mergers and acquisitions, whether they stay inside Canada or cross the border. Ian is a tax associate in Gowling WLG's Ottawa office, and the practice Ian is building takes in both Canadian and international tax. Clients can work with Ian in English or French, since Ian is fully fluent in both.

Engineering came first. Ian earned a chemical engineering degree at the University of Ottawa in 2019, picking up internships in the public and private sectors during those years, and then went to McGill for a BCL/JD, finishing in 2022. Ian started at Gowling WLG as a student-at-law, helping Ottawa corporate teams on acquisitions in 2023, and was called to the Ontario bar that same year.

That science background shows up in print. Before law, Ian co-wrote several peer-reviewed papers on organic electronics, along with research that came out of work with Canada's Department of National Defence. One of them, published in Dyes and Pigments in 2018 with Owen A. Melville, Nicole A. Rice and Benoît H. Lessard of the University of Ottawa's chemical engineering department, tested Hostasol Red GG, a cheap commercial pigment, as the semiconductor in organic thin-film transistors.

Ian keeps adding to that tax grounding. Ian is now working through the CPA Canada In-Depth Tax Program and writes regularly with the firm's Tax Group, from a 2024 piece on the new patent cost deduction to a November 2025 rundown of Canada's clean economy investment tax credits, co-written with tax practice leader Laura Gheorghiu.

Practice areas

Tax Law

Tax planning for financings, reorganizations and deals

Ian advises clients on the tax issues that come with raising financing, reorganizing a corporate group, and buying or selling a business, in both domestic and cross-border transactions. The practice covers Canadian and international tax alike.

Acquisitions and private equity transactions

As a student-at-law in 2023, Ian assisted on BESTECH's purchase of W.G. Spencer Engineering, a mining-sector engineering firm, and on Total HVAC's acquisition of Mastron Mechanical. Ian was also on the team for the founders of Decisive Group when Calian completed its acquisition in December 2023, and on the Canadian team for New York private equity firm Clarion Capital Partners when it bought Marketplace Events in January 2025.

Education & credentials

  • BCL/JD, McGill University (2022)
  • Bachelor of Engineering (Chemical), University of Ottawa (2019)
  • Called to the bar of Ontario (2023)

Publications & speaking

Memberships & affiliations

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This listing was generated by AI from public sources in October 2026. It may contain errors, and we can’t guarantee it’s accurate or complete. Before you rely on anything here, verify it on their firm’s website. Confirm Ian Therrien’s licence and standing in the Law Society of Ontario directory ↗

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