(1) Pension trusts (A) In general In the taxable year when paid, if the contributions are paid into a pension trust (other than a trust to which paragraph (3) applies), and if such taxable year ends within or with a taxable year of the trust for which the trust is exempt under section 501(a), in the case of a defined benefit plan other than a multiemployer plan, in an amount determined under subsection ( o ), and in the case of any other plan in an amount determined as follows: (i) the amount necessary to satisfy the minimum funding standard provided by section 412(a) for plan years ending within or with such taxable year (or for any prior plan year), if such amount is greater than the amount determined under clause (ii) or (iii) (whichever is applicable with respect to the plan), (ii) the amount necessary to provide with respect to all of the employees under the trust the remaining unfunded cost of their past and current service credits distributed as a level amount, or a level percentage of compensation, over the remaining future service of each such employee, as determined under regulations prescribed by the Secretary, but if such remaining unfunded cost with respect to any 3 individuals is more than 50 percent of such remaining unfunded cost, the amount of such unfunded cost attributable to such individuals shall be distributed over a period of at least 5 taxable years, (iii) an amount equal to the normal cost of the plan, as determined under regulations prescribed by the Secretary, plus, if past service or other supplementary pension or annuity credits are provided by the plan, an amount necessary to amortize the unfunded costs attributable to such credits in equal annual payments (until fully amortized) over 10 years, as determined under regulations prescribed by the Secretary. In determining the amount deductible in such year under the foregoing limitations the funding method and the actuarial assumptions used shall be those used for such year under section 431, and the maximum amount deductible for such year shall be an amount equal to the full funding limitation for such year determined under section 431. (B) Special rule in case of certain amendments In the case of a multiemployer plan which the Secretary of Labor finds to be collectively bargained which makes an election under this subparagraph (in such manner and at such time as may be provided under regulations prescribed by the Secretary), if the full funding limitation determined under section 431(c)(6) for such year is zero, if as a result of any plan amendment applying to such plan year, the amount determined under section 431(c)(6)(A)(ii) exceeds the amount determined under section 431(c)(6)(A)(i), and if the funding method and the actuarial assumptions used are those used for such year under section 431, the maximum amount deductible in such year under the limitations of this paragraph shall be an amount equal to the lesser of— (i) the full funding limitation for such year determined by applying section 431(c)(6) but increasing the amount referred to in subparagraph (A) thereof by the decrease in the present value of all unamortized liabilities resulting from such amendment, or (ii) the normal cost under the plan reduced by the amount necessary to amortize in equal annual installments over 10 years (until fully amortized) the decrease described in clause (i). In the case of any election under this subparagraph, the amount deductible under the limitations of this paragraph with respect to any of the plan years following the plan year for which such election was made shall be determined as provided under such regulations as may be prescribed by the Secretary to carry out the purposes of this subparagraph. (C) Certain collectively-bargained plans In the case of a plan which the Secretary of Labor finds to be collectively bargained, established or maintained by an employer doing business in not less than 40 States and engaged in the trade or business of furnishing or selling services described in section 168(i)(10)(C), with respect to which the rates have been established or approved by a State or political subdivision thereof, by any agency or instrumentality of the United States, or by a public service or public utility commission or other similar body of any State or political subdivision thereof, and in the case of any employer which is a member of a controlled group with such employer, subparagraph (B) shall be applied by substituting for the words “plan amendment” the words “plan amendment or increase in benefits payable under title II of the Social Security Act”. For the purposes of this subparagraph, the term “controlled group” has the meaning provided by section 1563(a), determined without regard to section 1563(a)(4) and (e)(3)(C). (D) Amount determined on basis of unfunded current liability In the case of a defined benefit plan which is a multiemployer plan, except as provided in regulations, the maximum amount deductible under the limitations of this paragraph shall not be less than the excess (if any) of— (i) 140 percent of the current liability of the plan determined under section 431(c)(6)(D), over (ii) the value of the plan’s assets determined under section 431(c)(2). (E) Carryover Any amount paid in a taxable year in excess of the amount deductible in such year under the foregoing limitations shall be deductible in the succeeding taxable years in order of time to the extent of the difference between the amount paid and deductible in each such succeeding year and the maximum amount deductible for such year under the foregoing limitations.