(a) If contributions are paid by an employer to or under a pension trust or annuity plan for employees and the general conditions and limitations applicable to deductions for such contributions are satisfied (see § 1.404(a)-1), the contributions are deductible under section 404(a) (1) or (2) if the further conditions provided therein are also satisfied. As used in this section, a “pension trust” means a trust forming part of a pension plan and an “annuity plan” means a pension plan under which retirement benefits are provided under annuity or insurance contracts without a trust. This section is also applicable to contributions to a foreign situs pension trust which could qualify for exemption under section 501(a) except that it is not created or organized and maintained in the United States. For the meaning of “pension plan” as used in this section, see paragraph (b)(1)(i) of § 1.401-1. Where disability pensions, insurance, or survivorship benefits incidental and directly related to the retirement benefits under a pension or annuity plan are provided for the employees or their beneficiaries by contributions under the plan, deductions on account of such incidental benefits are also covered under section 404(a) (1) or (2). See paragraph (b)(2) of § 1.72-16 as to taxability to employees of cost of incidental life insurance protection. Similarly, where medical benefits described in section 401(h) as defined in paragraph (a) of § 1.401-14 are provided for retired employees, their spouses, or their dependents under the plan, deductions on account of such subordinate benefits are also covered under section 404(a) (1) or (2). In order to be deductible under section 404(a)(1), contributions to a pension trust must be paid in a taxable year of the employer which ends with or within a year of the trust for which it is exempt under section 501(a). Contributions paid in such a taxable year of the employer may be carried over and deducted in a succeeding taxable year of the employer in accordance with section 404(a)(1)(D), whether or not such succeeding taxable year ends with or within a taxable year of the trust for which it is exempt under section 501(a). See § 1.404(a)-7 for rules relating to the limitation on the amount deductible in such a succeeding taxable year of the employer. See § 1.404(a)-8 as to conditions for deductions under section 404(a)(2) in the case of an annuity plan. In either case, the deductions are also subject to further limitations provided in section 404(a)(1). The limitations provided in section 404(a)(1) are, with an exception provided for certain years under subparagraph (A) thereof (see § 1.404(a)-4), based on the actuarial costs of the plan.

(b) In determining costs for the purpose of limitations under section 404(a)(1), the effects of expected mortality and interest must be discounted and the effects of expected withdrawals, changes in compensation, retirements at various ages, and other pertinent factors may be discounted or otherwise reasonably recognized. A properly weighted retirement age based on adequate analyses of representative experience may be used as an assumed retirement age. Different basic assumptions or rates may be used for different classes of risks or different groups where justified by conditions or required by contract. In no event shall costs for the purpose of section 404(a)(1) exceed costs based on assumptions and methods which are reasonable in view of the provisions and coverage of the plan, the funding medium, reasonable expectations as to the effects of mortality and interest, reasonable and adequate regard for other factors such as withdrawal and deferred retirement (whether or not discounted) which can be expected to reduce costs materially, reasonable expenses of operation, and all other relevant conditions and circumstances. In any case, in determining the costs and limitations, an adjustment shall be made on account of any experience more favorable than that assumed in the basis of limitations for prior years. Unless such adjustments are consistently made every year by reducing the limitations otherwise determined by any decrease in liability or cost arising from experience in the next preceding taxable year which was more favorable than the assumptions on which the costs and limitations were based, the adjustment shall be made by some other method approved by the Commissioner.

(c) The amount of a contribution to a pension or annuity plan that is deductible under section 404(a) (1) or (2) depends upon the methods, factors, and assumptions which are used to compute the costs of the plan and the limitation of section 404(a)(1) which is applied. Since the amount that is deductible for one taxable year may affect the amount that is deductible for other taxable years, the methods, factors, and assumptions used in determining costs and the method of determining the limitation which have been used for determining the deduction for a taxable year for which the return has been filed shall not be changed for such taxable year, except when the Commissioner determines that the methods, factors, assumptions, or limitations were not proper, or except when a change is necessitated by reason of the use of different methods, factors, assumptions, or limitations for another taxable year. However, different methods, factors, and assumptions, or a different method of determining the limitation, if they are proper, may be used in determining the deduction for a subsequent taxable year.

(d) Any expenses incurred by the employer in connection with the plan, such as trustee's and actuary's fees, which are not provided for by contributions under the plan are deductible by the employer under section 162 (relating to trade or business expenses), or 212 (relating to expenses for production of income) to the extent that they are ordinary and necessary.

(e) In case deductions are allowable under section 404(a)(3), as well as under section 404(a) (1) or (2), the limitations under section 404(a) (1) and (3) are determined and applied without giving effect to the provisions of section 404(a)(7) but the amounts allowable as deductions are subject to the further limitations provided in section 404(a)(7). See § 1.404(a)-13.