reduce period A rental reduction credit agency may provide a credit period for any qualified building which is less than 15 years. (3) Eligible unit (A) In general The term eligible unit means, with respect to any qualified building, a unit— (i) which is occupied by an eligible tenant, (ii) the rent of which for any month equals 30 percent of the monthly family income of the residents of such unit (as determined under paragraph (5)), (iii) with respect to which the tenant is not concurrently receiving rental assistance under any other Federal program, and (iv) which is certified to the rental reduction credit agency as an eligible unit for purposes of this section and the qualified rental reduction agreement. Notwithstanding clause (iii), a State may provide in its State rental reduction allocation plan that an eligible unit shall also not include a unit with respect to which any resident is receiving rental assistance under a State or local program. (B) Limitation on number of units (i) In general The number of units which may be certified as eligible units with respect to any qualified building under subparagraph (A)(iv) at any time shall not exceed the greater of— (I) 40 percent of the total units in such building, or (II) 25 units. In the case of an allocation to a project under subsection (c)(1)(B), the limitation under the preceding sentence shall be applied on a project basis and the certification of such eligible units shall be allocated to each building in the project, except that if buildings in such project are on non-contiguous tracts of land, buildings on each such tract shall be treated as a separate project for purposes of applying this sentence. (ii) Buildings receiving previous Federal rental assistance If, at any time prior to the entering into of a qualified rental reduction agreement with respect to a qualified building, tenants in units within such building had been receiving project-based rental assistance under any other Federal program, then, notwithstanding clause (i), the maximum number