floor space fraction
(1) Qualified basis (A) Determination The qualified basis of any qualified low-income building for any taxable year is an amount equal to— (i) the applicable fraction (determined as of the close of such taxable year) of (ii) the eligible basis of such building (determined under subsection (d)(5)). (B) Applicable fraction For purposes of subparagraph (A), the term “applicable fraction” means the smaller of the unit fraction or the floor space fraction. (C) Unit fraction For purposes of subparagraph (B), the term “unit fraction” means the fraction— (i) the numerator of which is the number of low-income units in the building, and (ii) the denominator of which is the number of residential rental units (whether or not occupied) in such building. (D) Floor space fraction For purposes of subparagraph (B), the term “floor space fraction” means the fraction— (i) the numerator of which is the total floor space of the low-income units in such building, and (ii) the denominator of which is the total floor space of the residential rental units (whether or not occupied) in such building. (E) Qualified basis to include portion of building used to provide supportive services for homeless In the case of a qualified low-income building described in subsection (i)(3)(B)(iii), the qualified basis of such building for any taxable year shall be increased by the lesser of— (i) so much of the eligible basis of such building as is used throughout the year to provide supportive services designed to assist tenants in locating and retaining permanent housing, or (ii) 20 percent of the qualified basis of such building (determined without regard to this subparagraph).