Margaret O'Sullivan's practice involves private client work, both domestic and multi-jurisdictional. Margaret is recognised in The Best Lawyers in Canada (2025), Legal Week's Private Client Global Elite 2025 and The Canadian Legal Lexpert Directory 2025 as a leading practitioner in estate planning; and in WWL: Private Client (2025) and WWL: Canada (2025) as one of the most highly regarded private client practitioners. She is ranked in band one of Chambers: High Net Worth Guide (2025) in private wealth law. She is the recipient of the 2014 STEP Founder's Award for Outstanding Achievement and the Ontario Bar Association's 2013 Award of Excellence in Trusts and Estates Law.
Margaret is a former deputy chair and member of the board of directors and council for STEP Worldwide, and a former chair of its professional standards committee. She is a founding member and a former deputy chair of the Society of Trust and Estate Practitioners (Canada) and former chair of the editorial board of its newsletter Step Inside. She is a former chair of the Trusts and Estates Section of the Ontario Bar Association, and a past elected member of the Ontario Bar Association Council (1993–1998). She is an academician of the International Academy of Estate and Trust Law, and fellow of the American College of Trust and Estate Counsel...
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Margaret O'Sullivan is "a clear leader" in the field of private client work, with a standout practice focused on high-net-worth succession planning. Her extensive expertise spans domestic and multijurisdictional trust and estate matters, earning her recognition for top-tier counsel across complex planning, litigation, and administration issues.