The word “undertaking”, when used outside of the legal setting, has many meanings: “the management of funerals”; “the act of engaging in a project or business”; “a promise, pledge or guarantee”. When used in law, the word undertaking often has a meaning similar to “promise, pledge, or guarantee”, but express undertakings given by lawyers are more significant than regular promises, pledges, or guarantees, because in addition to being liable for breach of contract a lawyer breaching an undertaking may be subject to disciplinary action by the professional body that regulates lawyers in the relevant jurisdiction.
Lawyers often give express undertakings (e.g. to not release funds to their client until certain documents are signed and / or filed) and breach of such express undertakings may be a breach of professional ethics: Law Society of British Columbia Professional Conduct Handbook, s. 11-7.
Implied undertakings are different to express undertakings because they arise without any positive agreement by the party to be bound: the implied undertaking rule automatically applies when one party to litigation discloses information related to the dispute to another party to the litigation under compulsion of the Rules of Court. According to the implied undertaking rule lawyers and their clients are bound to keep information disclosed under compulsion of the rules of court confidential and to not use it for a collateral purpose unless with the disclosing party’s permission or leave of the court.
Although some provinces have codified implied undertakings, they exist at common law. In Goodman v. Rossi, 1995 CanLII 1888 (Ont. CA) the Ontario Court of Appeal noted that all Canadian jurisdictions that have considered whether implied undertakings should be imposed at common law have held that they should. More recently, the Supreme Court of Canada cases of Lac d'Amiante du Québec Ltée v. 2858-0702 Québec Inc., 2001 SCC 51 and Juman v. Doucette, 2008 SCC 8 confirmed the existence of implied undertakings at common law.