credit period
(1) Credit period defined For purposes of this section, the term “credit period” means, with respect to any building, the period of 10 taxable years beginning with— (A) the taxable year in which the building is placed in service, or (B) at the election of the taxpayer, the succeeding taxable year, but only if the building is a qualified low-income building as of the close of the 1st year of such period. The election under subparagraph (B), once made, shall be irrevocable.