Except as otherwise provided in this section, any mutual insurance company which is an interinsurer or reciprocal underwriter (hereinafter in this section referred to as a “reciprocal”) subject to the taxes imposed by section
831
(a) may, under regulations prescribed by the Secretary, elect to be subject to the limitation provided in subsection (b). Such election shall be effective for the taxable year for which made and for all succeeding taxable years, and shall not be revoked except with the consent of the Secretary.