(a) An election under section 307¹ may be revoked if shareholders holding more than one-half of the shares of stock of the corporation on the day on which the revocation is made consent to the revocation. The corporation and any successor corporation shall not be eligible to revoke an election under this section for any taxable year prior to its fifth taxable year which begins after the first taxable year for which an election is effective unless the corporation becomes a qualified Subchapter S subsidiary.

(b) A revocation under subsection (a) shall be effective on the first day of the taxable year if made on or before the fifteenth day of the third month thereof; if the revocation is made after such date, it shall be effective for the following taxable year.