((a)) ** Allowance of deduction** There is allowed as a deduction for the taxable year an amount equal to the sum of the amounts contributed by the taxpayer during the taxable year to or under a trust or trusts described in section 501(c)(21).
((b)) ** Limitation** The maximum amount of the deduction allowed by subsection (a) for any taxpayer for any taxable year shall not exceed the greater of—
((1)) the amount necessary to fund (with level funding) the remaining unfunded liability of the taxpayer for black lung claims filed (or expected to be filed) by (or with respect to) past or present employees of the taxpayer, or
((2)) the aggregate amount necessary to increase each trust described in section 501(c)(21) to the amount required to pay all amounts payable out of such trust for the taxable year.
((c)) ** Special rules**
((1)) ** Method of determining amounts referred to in subsection (b)**
((A)) ** In general** The amounts described in subsection (b) shall be determined by using reasonable actuarial methods and assumptions which are not inconsistent with regulations prescribed by the Secretary.
((B)) ** Funding period** Except as provided in subparagraph (C), the funding period for purposes of subsection (b)(1) shall be the greater of—
((i)) the average remaining working life of miners who are present employees of the taxpayer, or
((ii)) 10 taxable years.
((C)) ** Different funding periods** To the extent that—
((i)) regulations prescribed by the Secretary provide for a different period, or
((ii)) the Secretary consents to a different period proposed by the taxpayer,
((2)) ** Benefit payments taken into account** In determining the amounts described in subsection (b), only those black lung benefit claims the payment of which is expected to be made from the trust shall be taken into account.
((3)) ** Time when contributions deemed made** For purposes of this section, a taxpayer shall be deemed to have made a payment of a contribution on the last day of a taxable year if the payment is on account of that taxable year and is made not later than the time prescribed by law for filing the return for that taxable year (including extensions thereof).
((4)) ** Contributions to be in cash or certain other items** No deduction shall be allowed under subsection (a) with respect to any contribution to a trust described in section 501(c)(21) other than a contribution in cash or in items in which such trust may invest under subclause (II) of section 501(c)(21)(A)(ii).
((5)) ** Denial of section 162 deduction with respect to liability** No deduction shall be allowed under section 162(a) with respect to any liability taken into account in determining the deduction under subsection (a) of this section of the taxpayer (or a predecessor).
((d)) ** Carryover of excess contributions** If the amount of the deduction determined under subsection (a) for the taxable year (without regard to the limitation imposed by subsection (b)) with respect to a trust exceeds the limitation imposed by subsection (b) for the taxable year, the excess shall be carried over to the succeeding taxable year and treated as contributed to the trust during that year.
((e)) ** Definition of black lung benefit claim** For purposes of this section, the term “black lung benefit claim” means a claim for compensation for disability or death due to pneumoconiosis under part C of title IV of the Federal Mine Safety and Health Act of 1977 or under any State law providing for such compensation.