to a property the basis of which is affected by a qualified casualty loss until the period described in clause (i) (as modified by clause (ii), if applicable) with respect to such property has expired. (iv) Qualified casualty loss For purposes of this subparagraph, the term qualified casualty loss means a casualty loss that is the result of a Federally declared disaster (as defined in section 165(i)(5)). . (b) Qualified basis following casualty loss Paragraph (1) of section 42(c) of the Internal Revenue Code of 1986 is amended by adding at the end the following new subparagraph: (F) Qualified basis following casualty loss If a casualty causes the qualified basis of a building in any year to be less than the qualified basis in the immediately preceding year then, in the year of such casualty and each succeeding year until such building or the units affected by the casualty are reconstructed or replaced (but only through the last year of the period permitted for reconstruction or replacement under subsection (j)(4)(E))— (i) the qualified basis of such building shall be equal to the qualified basis of such building as of the last day of the year preceding the year in which such casualty occurred, (ii) if such building is not reconstructed or replaced by the expiration of the applicable period for such reconstruction or replacement under subsection (j)(4), then the recapture amount provided for in subsection (j)(1) shall include the amount of any credit claimed under this section by reason of the application of clause (i), and (iii) a building which was a qualified low-income building as of the last day of the year preceding the year in which such casualty occurred shall not cease to be a qualified low-income building solely because of such casualty. . (c) Effective date The amendments made by this section shall apply to casualties occurring after the date which is 25 months before the date of the enactment of this Act. 302. Modification of previous ownership rules