Ms Margaret O'Sullivan

Membership category: Full Member i

'TEP' status denotes full membership of STEP and is the top level of STEP membership. TEPs are fully qualified practitioners with proven qualifications and experience. They can use the letters 'TEP' after their name. TEPs must adhere to STEP's Code of Professional Conduct.

TD Bank Tower
#3430 - 66 Wellington St W
P.O.Box 68
M5K 1E7

Telephone: +1 416 3633700
Practice Areas: Charity formation/administration, Contentious trusts and estates, Cross-border estates, Elderly and vulnerable clients, Estate planning/administration, Philanthropy, Tax, Trust planning/administration, Wills and probate
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O'Sullivan Estate Lawyers
STEP Toronto
Cross-Border Estates SIG Steering Committee, STEP Canada Awards Committee
Special Interest Groups:
Cross-Border Estates | Mental Capacity

Law Practice

Margaret O'Sullivan's practice involves all aspects of private client work, including estate planning; will and trust planning; incapacity planning; estate litigation; advising executors, trustees and beneficiaries and administration of estates and trusts. Margaret is recognized in The Best Lawyers in Canada 2017, in the 2016 Edition of The Canadian Legal Lexpert Directory as a leading practitioner in estate planning, in The Who’s Who Legal: Private Client 2016, and in The Who’s Who Legal: Canada 2016 as one of the most highly regarded private client practitioners. She is one of six top-ranked private client lawyers in Chambers Canada Guide 2017 and a top-ranked private wealth lawyer in Chambers High Net Worth Guide 2016, and 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. Prior to establishing an independent practice, Margaret was a partner in the Toronto office of the national Canadian law firm Stikeman Elliott where she directed its trusts and estates practice. She has practiced exclusively in the area of trusts and estates since 1983.

Professional Activities

Margaret 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 past Deputy Chair and past member of the Board of Directors and Council for STEP Worldwide as well as a past Chair of the Professional Standards Committee. She is a past 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, as well as a current member of the Canadian Bar Association, the American Bar Association, the New York State Bar Association, the International Bar Association, and the Canadian Tax Foundation. She was elected a Fellow of the American College of Trust and Estate Counsel in 1995 and elected as a member of the STEP Cross Border Estates Global Steering Committee in 2017.  Margaret is also a current member of the Queen's University Gift Planning Advisory Committee.


Margaret has been a frequent guest speaker, writer and conference chairperson for various professional organizations on the subject of trusts and estates, including for the Society of Trust and Estate Practitioners, the Canadian Bar Association, The Law Society of Upper Canada, The International Bar Association, the Canadian Tax Foundation and various private conference sponsors. She has also written extensively in the areas of trusts, estate planning, estate administration and estate litigation. She is past editor and contributor to the Ontario Bar Association - Trusts and Estates Section Newsletter. Margaret authored two textbooks and developed the courses Engineering of a Trust and Trust and Estate Management for the Trust Institute of the Institute of Canadian Bankers. She is a co-author, Canada Chapter, International Succession Laws (Tottel 2009), and a contributing author to Widdifield on Executors and Trustees (Carswell 2002), The Private Wealth & Private Client Review (Law Business Research 2016), The International Comparative Legal Guide to: Private Client 2017 (Global Legal Group 2016), Practical Law's Private Client Global Guide 2016/17 (Thomson Reuters) and Lexis Practice Advisor Canada (LexisNexis).


Margaret graduated from Queens University, B.A. 1978 (magna cum laude) and LL.B. 1981. In 1983, she was called to the Ontario Bar.

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