(1)In general: after 1983 and before April 1, 1991. In the case of a calendar month which begins after December 31, 1983, and before April 1, 1991, if, at a time prescribed under § 31.6302(c)-1(a)(1) (i) or (v) for the deposit of undeposited taxes, the aggregate amount of undeposited employee tax withheld after December 31, 1983, and before April 1, 1991, under section 3202 and employer tax imposed after December 31, 1983, and before April 1, 1991, under section 3221(a) and (b) equals an amount required to be deposited under § 31.6302(c)-1(a)(1) (i) or (v) the employer shall deposit the undeposited railroad retirement taxes described in sections 3202 and 3221 at such time in the manner prescribed in § 31.6302(c)-1(a)(1) (i) or (v) (except that undeposited railroad retirement taxes described in section 3221 (c) shall in no case be required to be deposited earlier than the first day on which a deposit is otherwise required by § 31.6302(c)-1(a)(1)(i) to be made after the 15th day of the month following the month in which the section 3221 (c) tax arises). Notwithstanding the preceding sentence, and notwithstanding subdivision (v) of § 31.6302 (c)-1 (a) (1) , if, for the calendar year prior to the calendar year preceding the current calendar year, the aggregate amount of taxes imposed under sections 3202 and 3221 with respect to an employer equalled or exceeded $1 million, such employer shall deposit his undeposited railroad retirement taxes required to be deposited for the current calendar year in accordance with Revenue Procedure 83-90, 1983-52 I.R.B. 18, (relating to transfers by wire to the Treasury).