allowed
(i) For purposes of subparagraph (1) of this paragraph, generally all deductions (described in subparagraph (2) of this paragraph) allowed or allowable shall be taken into account. See section 1016(a)(2) and the regulations thereunder for the meaning of allowed and allowable. However, if a taxpayer can establish by adequate records or other sufficient evidence that the amount allowed for any period was less than the amount allowable for such period, the amount to be taken into account for such period shall be the amount allowed. The preceding sentence shall not apply for purposes of computing under paragraph (b)(1)(ii) of this section the amount such deductions would have been under the straight line method.