29 CFR § 4006.3 - Premium rate.
Subject to the provisions of § 4006.5 (dealing with exemptions and special rules) and § 4006.7 (dealing with premiums for certain terminated single-employer plans), the premium paid for basic benefits guaranteed under section 4022(a) or section 4022A(a) of ERISA shall equal the flat-rate premium under paragraph (a) of this section plus, in the case of a single-employer plan, the variable-rate premium under paragraph (b) of this section. Premium rates (and the MAP–21 cap rate referred to in paragraph (b)(2) of this section) are subject to change each year under inflation indexing provisions in section 4006 of ERISA.
(a) Flat-rate premium. The flat-rate premium for a plan is equal to the applicable flat premium rate multiplied by the plan's participant count. The applicable flat premium rate is the amount prescribed for the calendar year in which the premium payment year begins by the applicable provisions of—
(1) Section 4006(a)(3)(A) and (G) of ERISA for a single-employer plan, or
(2) Section 4006(a)(3)(A) and (J) of ERISA for a multiemployer plan.
(b) Variable-rate premium—(1) In general. Subject to the cap provisions in paragraphs (b)(2) and (b)(3) of this section, the variable-rate premium for a single-employer plan is equal to a specified dollar amount for each $1,000 (or fraction thereof) of the plan's unfunded vested benefits as determined under § 4006.4 for the UVB valuation year. The specified dollar amount is the applicable variable premium rate prescribed by the applicable provisions of ERISA section 4006(a)(8) for the calendar year in which the premium payment year begins.
(2) MAP–21 cap. The variable-rate premium for a plan is not more than the applicable MAP–21 cap rate multiplied by the plan's participant count. The applicable MAP–21 cap rate is the amount prescribed by the applicable provisions of ERISA section 4006(a)(3)(E)(i)(II), (E)(i)(III), (K), and (L) for the calendar year in which the premium payment year begins.
(3) Small-employer cap.
(i) In general. If a plan is described in paragraph (b)(3)(ii) of this section for the premium payment year, the variable-rate premium is not more than $5 multiplied by the square of the participant count. For example, if the participant count is 20, the variable-rate premium is not more than $2,000 ($5 × 20 2 = $5 × 400 = $2,000).
(ii) Plans eligible for cap. A plan is described in paragraph (b)(3)(ii) of this section for the premium payment year if the aggregate number of employees of all employers in the plan's controlled group on the first day of the premium payment year is 25 or fewer.
(iii) Meaning of “employee.” For purposes of paragraph (b)(3)(ii) of this section, the aggregate number of employees is determined in the same manner as under section 410(b)(1) of the Code, taking into account the provisions of section 414(m) and (n) of the Code, but without regard to section 410(b)(3), (4), and (5) of the Code.