Revision of Advance Pricing Agreements may occur for changed assumptions or law, with prescribed procedure and possible cancellation. An Advance Pricing Agreement may be revised by the Board for changes in critical assumptions, failure to meet conditions, changes in law that modify covered matters, or at the request of a foreign competent authority. Revision may be suo moto or on request; except where the assessee requests revision, the assessee must be heard and must agree, otherwise the agreement may be cancelled. The Board must give written reasons if it rejects an assessee's request. The revision process may follow the scheme's consultation procedures and must state effective dates for the original and revised agreements.