Subsection (b) applies to—

(1) a plan maintained pursuant to an agreement which the Secretary of Labor finds to be a collective-bargaining agreement between employee representatives and one or more employers, and

(2) each trust which is a part of such plan.

If this subsection applies to a plan, notwithstanding any other provision of this title—

(1) Participation Section 410 shall be applied as if all employees of each of the employers who are parties to the collective-bargaining agreement and who are subject to the same benefit computation formula under the plan were employed by a single employer.

(2) Discrimination, etc. Sections 401(a)(4) and 411(d)(3) shall be applied as if all participants who are subject to the same benefit computation formula and who are employed by employers who are parties to the collective bargaining agreement were employed by a single employer.

(3) Exclusive benefit For purposes of section 401(a), in determining whether the plan of an employer is for the exclusive benefit of his employees and their beneficiaries, all plan participants shall be considered to be his employees.

(4) Vesting Section 411 (other than subsection (d)(3)) shall be applied as if all employers who have been parties to the collective-bargaining agreement constituted a single employer, except that the application of any rules with respect to breaks in service shall be made under regulations prescribed by the Secretary of Labor.

(5) Funding The minimum funding standard provided by section 412 shall be determined as if all participants in the plan were employed by a single employer.

For a plan year the liability under section 4971 of each employer who is a party to the collective bargaining agreement shall be determined in a reasonable manner not inconsistent with regulations prescribed by the Secretary—

(A) first on the basis of their respective delinquencies in meeting required employer contributions under the plan, and

(B) then on the basis of their respective liabilities for contributions under the plan.

(7) Deduction limitations Each applicable limitation provided by section 404(a) shall be determined as if all participants in the plan were employed by a single employer. The amounts contributed to or under the plan by each employer who is a party to the agreement, for the portion of his taxable year which is included within such a plan year, shall be considered not to exceed such a limitation if the anticipated employer contributions for such plan year (determined in a manner consistent with the manner in which actual employer contributions for such plan year are determined) do not exceed such limitation. If such anticipated contributions exceed such a limitation, the portion of each such employer’s contributions which is not deductible under section 404 shall be determined in accordance with regulations prescribed by the Secretary.

(8) Employees of labor unions For purposes of this subsection, employees of employee representatives shall be treated as employees of an employer described in subsection (a)(1) if such representatives meet the requirements of sections 401(a)(4) and 410 with respect to such employees.

(9) Plans covering a professional employee Notwithstanding subsection (a), in the case of a plan (and trust forming part thereof) which covers any professional employee, paragraph (1) shall be applied by substituting “section 410(a)” for “section 410”, and paragraph (2) shall not apply.

In the case of a plan maintained by more than one employer—

(1) Participation Section 410(a) shall be applied as if all employees of each of the employers who maintain the plan were employed by a single employer.

(2) Exclusive benefit For purposes of section 401(a), in determining whether the plan of an employer is for the exclusive benefit of his employees and their beneficiaries all plan participants shall be considered to be his employees.

(3) Vesting Section 411 shall be applied as if all employers who maintain the plan constituted a single employer, except that the application of any rules with respect to breaks in service shall be made under regulations prescribed by the Secretary of Labor.

In the case of a plan established after December 31, 1988, each employer shall be treated as maintaining a separate plan for purposes of section 412 unless such plan uses a method for determining required contributions which provides that any employer contributes not less than the amount which would be required if such employer maintained a separate plan.

(A) In general In the case of a plan established after December 31, 1988, each employer shall be treated as maintaining a separate plan for purposes of section 412 unless such plan uses a method for determining required contributions which provides that any employer contributes not less than the amount which would be required if such employer maintained a separate plan.

(B) Other plans In the case of a plan not described in subparagraph (A), the requirements of section 412 shall be determined as if all participants in the plan were employed by a single employer unless the plan administrator elects not later than the close of the first plan year of the plan beginning after the date of enactment of the Technical and Miscellaneous Revenue Act of 1988 to have the provisions of subparagraph (A) apply. An election under the preceding sentence shall take effect for the plan year in which made and, once made, may be revoked only with the consent of the Secretary.

For a plan year the liability under section 4971 of each employer who maintains the plan shall be determined in a reasonable manner not inconsistent with regulations prescribed by the Secretary—

(A) first on the basis of their respective delinquencies in meeting required employer contributions under the plan, and

(B) then on the basis of their respective liabilities for contributions under the plan.

In the case of a plan established after December 31, 1988, each applicable limitation provided by section 404(a) shall be determined as if each employer were maintaining a separate plan.

(A) In general In the case of a plan established after December 31, 1988, each applicable limitation provided by section 404(a) shall be determined as if each employer were maintaining a separate plan.

(B) Other plans (i) In general In the case of a plan not described in subparagraph (A), each applicable limitation provided by section 404(a) shall be determined as if all participants in the plan were employed by a single employer, except that if an election is made under paragraph (4)(B), subparagraph (A) shall apply to such plan. (ii) Special rule If this subparagraph applies, the amounts contributed to or under the plan by each employer who maintains the plan (for the portion of the taxable year included within a plan year) shall be considered not to exceed any such limitation if the anticipated employer contributions for such plan year (determined in a reasonable manner not inconsistent with regulations prescribed by the Secretary) do not exceed such limitation. If such anticipated contributions exceed such a limitation, the portion of each such employer’s contributions which is not deductible under section 404 shall be determined in accordance with regulations prescribed by the Secretary.

Except as provided in subparagraph (B), allocations of amounts under paragraphs (4), (5), and (6) among the employers maintaining the plan shall not be inconsistent with regulations prescribed for this purpose by the Secretary.

(A) In general Except as provided in subparagraph (B), allocations of amounts under paragraphs (4), (5), and (6) among the employers maintaining the plan shall not be inconsistent with regulations prescribed for this purpose by the Secretary.

(B) Assets and liabilities of plan For purposes of applying paragraphs (4)(A) and (6)(A), the assets and liabilities of each plan shall be treated as the assets and liabilities which would be allocated to a plan maintained by the employer if the employer withdrew from the multiple employer plan.

Notwithstanding any other provision of this section, in the case of a CSEC plan—

(1) Funding The requirements of section 412 shall be determined as if all participants in the plan were employed by a single employer.

(2) Application of provisions Paragraphs (1), (2), (3), and (5) of subsection (c) shall apply.

(3) Deduction limitations Each applicable limitation provided by section 404(a) shall be determined as if all participants in the plan were employed by a single employer. The amounts contributed to or under the plan by each employer who maintains the plan (for the portion of the taxable year included within a plan year) shall be considered not to exceed such applicable limitation if the anticipated employer contributions for such plan year of all employers (determined in a reasonable manner not inconsistent with regulations prescribed by the Secretary) do not exceed such limitation. If such anticipated contributions exceed such limitation, the portion of each such employer’s contributions which is not deductible under section 404 shall be determined in accordance with regulations prescribed by the Secretary.

(4) Allocations Allocations of amounts under paragraph (3) and subsection (c)(5) among the employers maintaining the plan shall not be inconsistent with the regulations prescribed for this purpose by the Secretary.

(Added Pub. L. 93–406, title II, § 1014, Sept. 2, 1974, 88 Stat. 924; amended Pub. L. 94–455, title XIX, § 1906(b)(13)(A), Oct. 4, 1976, 90 Stat. 1834; Pub. L. 96–364, title II, § 208(d), Sept. 26, 1980, 94 Stat. 1290; Pub. L. 100–647, title I, § 1011(h)(10), title VI, § 6058(a)–(c), Nov. 10, 1988, 102 Stat. 3466, 3698, 3699; Pub. L. 101–508, title XI, § 11704(a)(4), Nov. 5, 1990, 104 Stat. 1388–518; Pub. L. 113–97, title II, § 202(b), Apr. 7, 2014, 128 Stat. 1134; Pub. L. 115–141, div. U, title IV, § 401(a)(86), Mar. 23, 2018, 132 Stat. 1188.)