(1)Subsection (2) applies if an advance pricing agreement provides for the modification, or revocation, of the agreement—
(a)by the Commissioners, or
(b)by an officer.
(2)The agreement may provide for the modification or revocation to take effect as from such time as the Commissioners or officer may determine.
(3)A time determined under subsection (2) may be (but need not be) a time before the modification is made or the agreement is revoked.