B-1, r. 3.1 - Code of Professional Conduct of Lawyers

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99. A lawyer must, before agreeing with the client to provide professional services, ensure that the client has all useful information regarding his financial terms and obtain his consent thereto, except if he has reason to believe that the client is already informed thereof.
During the course of the mandate, the lawyer must keep the client informed of circumstances that could entail significant changes to the anticipated cost of his professional services.
O.C. 129-2015, s. 99.