26 C.F.R. § 1.404(a)-1T
Q-1: How does the amendment of section 404(b) by the Tax Reform Act of 1984 affect the deduction of contributions or compensation under section 404(a)?
A-1: As amended by the Tax Reform Act of 1984, section 404(b) clarifies that section 404(a) shall govern the deduction of contributions paid and compensation paid or incurred by the employer under a plan, or method or arrangement, deferring the receipt of compensation or providing for deferred benefits to employees, their spouses, or their dependents. See section 404(b) and § 1.404(b)-1T . Section 404 (a) and (d) requires that such a contribution or compensation be paid or incurred for purposes of section 162 or 212 and satisfy the requirements for deductibility under either of those sections. However, notwithstanding the above, section 404 does not apply to contributions paid or accrued with respect to a "welfare benefit fund" (as defined in section 419(e)) after July 18, 1984, in taxable years of employers (and payors) ending after that date. Also, section 463 shall govern the deduction of vacation pay by a taxpayer that has elected the application of such section. For rules relating to the deduction of contributions paid or accured with respect to a welfare benefit fund, see section 419, § 1.419-1T and § 1.419A-2T . For rules relating to the deduction of vacation pay for which an election is made under section 463, see § 301.9100-16T of this chapter and § 1.463-1T .
26 C.F.R. §1.404(a)-1T