applicable portion
(4) Failure to fully repay (A) In general To the extent that the requirements of paragraph (2)(D) are not met, then the taxpayer’s tax under this chapter for the taxable year in which such failure occurs shall be increased by an amount equal to the applicable portion of the credit under this section with respect to such building, increased by an amount of interest for the period— (i) beginning with the due date for the filing of the return of tax imposed by chapter 1 for the 1st taxable year for which such credit was allowable, and (ii) ending with the due date for the taxable year in which such failure occurs, determined by using the underpayment rate and method under section 6621. (B) Applicable portion For purposes of subparagraph (A), the term “applicable portion” means the aggregate decrease in the credits allowed to a taxpayer under section 38 for all prior taxable years which would have resulted if the eligible basis of the building were reduced by the amount of financing which does not meet requirements of paragraph (2)(D). (C) Certain rules to apply Rules similar to the rules of subparagraphs (A) and (D) of subsection (j)(4) shall apply for purposes of this subsection.