against the tax imposed by this subtitle for the taxable year an amount equal to 50 percent of the lead hazard reduction activity cost paid or incurred by the taxpayer during the taxable year for each eligible dwelling unit. (2) Election to apply costs to prior year For purposes of this section, a taxpayer may elect to treat any lead hazard reduction activity cost paid or incurred by the taxpayer during the taxable year as having been paid or incurred during the preceding taxable year. (b) Limitations (1) In general Subject to paragraph (3), the amount of the credit allowed under subsection (a) for any eligible dwelling unit for any taxable year shall not exceed— (A) $3,000 in the case of lead hazard reduction activity cost including lead abatement measures described in clauses (i), (ii), (iv), and (v) of subsection (c)(1)(A), or (B) $1,000 in the case of lead hazard reduction activity cost including interim lead control measures described in clauses (i), (iii), (iv), and (v) of subsection (c)(1)(A). (2) Other tax credits In the case of any credit against State or local tax liabilities which is allowable under the laws of any State or political subdivision thereof to a taxpayer with respect to any costs paid or incurred by the taxpayer which would otherwise qualify as lead hazard reduction activity costs under this section (referred to in this paragraph as the State or local tax credit amount ), the amount of the credit allowed under subsection (a) for any eligible dwelling unit for any taxable year (determined after application of paragraph (1)) shall not exceed an amount equal to the difference between— (A) the lead hazard reduction activity cost paid or incurred by the taxpayer during the taxable year for such unit, and (B) the State or local tax credit amount. (3) Limitation per residence The cumulative amount of the credit allowed under subsection (a) for an eligible dwelling unit for all taxable years shall not exceed $4,000. (c) Definitions and special rules For purposes of this section: (1) Lead hazard