For purposes of applying the limitations of subsections (b) and (c)--
(A) all defined benefit plans (whether or not terminated) of an employer are to be treated as one defined benefit plan, and
(B) all defined contribution plans (whether or not terminated) of an employer are to be treated as one defined contribution plan.
If the employer has more than one defined benefit plan--
(A) subsection (b)(1)(B) shall be applied separately with respect to each such plan, but
(B) in applying subsection (b)(1)(B) to the aggregate of such defined benefit plans for purposes of this subsection, the high 3 years of compensation taken into account shall be the period of consecutive calendar years (not more than 3) during which the individual had the greatest aggregate compensation from the employer.
Notwithstanding paragraph (1) and subsection (g), a multiemployer plan (as defined in section 414(f)) shall not be combined or aggregated --
(A) with any other plan which is not a multiemployer plan for purposes of applying subsection (b)(1)(B) to such other plan, or
(B) with any other multiemployer plan for purposes of applying the limitations established in this section.
Except as provided in subsection (f)(3), the Secretary, in applying the provisions of this section to benefits or contributions under more than one plan maintained by the same employer, and to any trusts, contracts, accounts, or bonds referred to in subsection (a)(2), with respect to which the participant has the control required under section 414(b) or (c), as modified by subsection (h), shall, under regulations prescribed by the Secretary, disqualify one or more trusts, plans, contracts, accounts, or bonds, or any combination thereof until such benefits or contributions do not exceed the limitations contained in this section. In addition to taking into account such other factors as may be necessary to carry out the purposes of subsection (f), the regulations prescribed under this paragraph shall provide that no plan which has been terminated shall be disqualified until all other trusts, plans, contracts, accounts, or bonds have been disqualified.
For purposes of applying subsections (b) and (c) of section 414 to this section, the phrase "more than 50 percent" shall be substituted for the phrase "at least 80 percent" each place it appears in section 1563(a)(1).
For purposes of this section, any annuity contract described in section 403(b) for the benefit of a participant shall be treated as a defined contribution plan maintained by each employer with respect to which the participant has the control required under subsection (b) or (c) of section 414 (as modified by subsection (h)). For purposes of this section, any contribution by an employer to a simplified employee pension plan for an individual for a taxable year shall be treated as an employer contribution to a defined contribution plan for such individual for such year.