C-48.1, r. 6 - Code of ethics of chartered professional accountants

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59.4. A member who charges a contingent fee shall have agreed with the client in writing on the basis for determining the fee before he begins to perform the professional services.
If the nature of the professional services changes while they are being performed, the member shall reassess whether the conditions set out in sections 59.1 and 59.2 are still met.
O.C. 779-2004, s. 23.