Revocation of a power of attorney becomes effective on the date that the revocation is RECEIVED in the Office (not on the date of ACCEPTANCE). Upon revocation of the power of attorney, appropriate notification is sent by the Office. While an application is involved in an interference or derivation proceeding, any power of attorney or revocation of power of attorney should be forwarded to the Patent Trial and Appeal Board for consideration. See MPEP § 402.08.
See MPEP § 402.05(a) for applicant revocation of powers of attorney in applications filed on or after September 16, 2012. See MPEP § 402.05(b) for applicant revocation of powers of attorney in applications filed before September 16, 2012. See MPEP § 402.07 for assignee revocation of a power of attorney.