Nothing in this paragraph shall allow an item to be deducted more than once.
businesses in which coupons were issued. Third, either before or after an amendment to the taxpayer's tax returns as described in paragraph (d) of this section, a method of accounting reasonably similar to the method of accounting described in § 1.451-4 must have been used for the taxable year ending on or before December 31, 1978. If these conditions are met, the taxpayer will treat the election of the method under section 466 as a change in method of accounting to which the rules in section 481 and the regulations thereunder apply.
26 C.F.R. §1.466-2