29 U.S.C. § 1321 — Coverage

(a) Plans covered. Except as provided in subsection (b), this subchapter applies to a plan, including a successor plan, that for a plan year^*: (1) is an employee pension benefit plan, as defined in section 1002(2), established or maintained (A) by an employer engaged in commerce or an industry or activity affecting commerce, (B) by an employee organization or organization representing employees engaged in that commerce or activity, or (C) by both, and that has, in practice, met the requirements of part I of subchapter D of chapter 1 of title 26 that apply to the plans described in paragraph (2), for the preceding five plan years of the plan; or (2) is, or has been determined by the Treasury Secretary to be, a plan described in section 401(a) of title 26, or meets, or has been determined by that Secretary to meet, section 404(a)(2) of title 26. A successor plan is treated as a continuation of its predecessor. Unless this subchapter specifically says otherwise, a successor plan is one covering substantially the same employees as the earlier plan and providing substantially the same benefits.

(b) Plans not covered. This section does not apply to a plan: (1) that is an individual account plan, as defined in section 1002(34); (2) established and maintained for government employees by the United States, a State, or a political subdivision, agency, or instrumentality, or a plan to which the Railroad Retirement Act of 1935 or 1937 applies and that is financed by required contributions, or a plan described in the last sentence of section 1002(32); (3) that is a church plan as defined in section 414(e), unless it elects coverage under section 410(d) and notifies the corporation as required; (4)(A) established and maintained by a society, order, or association described in section 501(c)(8) or (9), if employers of participants make no contributions to or under it, or (B) of which a section 501(c)(18) trust is part; (5) that has never provided for employer contributions at any time after September 2, 1974; (6) that is unfunded and maintained mainly to provide deferred compensation for a select group of management or highly compensated employees; (7) established and maintained outside the United States mainly for people who are substantially all nonresident aliens; (8) maintained by an employer only to provide benefits above the contribution and benefit limits in section 415, whether funded or not, including any separable part maintained for that purpose, which is treated as a separate excess-benefit plan; (9) established and maintained only for substantial owners; (10) of an international organization exempt from tax under the International Organizations Immunities Act; (11) maintained only to comply with workers' compensation, unemployment-compensation, or disability-insurance laws; (12) that is a defined-benefit plan treated as an individual account plan under section 1002(35)(B); or (13) established and maintained by a professional-service employer that has not had more than 25 active participants at any time after September 2, 1974.

(c) Definitions. (1) For subsection (b)(1), “individual account plan” does not include a plan promising a fixed benefit if the employer or the employer's representative participated in determining that benefit. This section does not otherwise define “individual account plan.”
(2) For this paragraph and subsection (b)(13), (A) “professional service employer” means a proprietorship, partnership, corporation, or other association or organization (i) owned or controlled by professional individuals or their executors or administrators and (ii) whose main business is performing professional services. (B) “Professional individuals” includes, but is not limited to, physicians, dentists, chiropractors, osteopaths, optometrists, other licensed healing-art practitioners, lawyers, public accountants, public engineers, architects, draftsmen, actuaries, psychologists, social or physical scientists, and performing artists.
(3) A plan established and maintained by more than one professional-service employer is not treated as a plan described in subsection (b)(13) if, at any time after September 2, 1974, it has more than 25 active participants.

(d) Substantial owner defined. For subsection (b)(9), “substantial owner” means an individual who, at any time during the 60-month period ending on the date of the determination: (1) owns the entire interest in an unincorporated trade or business; (2) in a partnership, directly or indirectly owns more than 10 percent of the capital interest or profits interest; or (3) in a corporation, directly or indirectly owns more than 10 percent in value of the corporation's voting stock or all of its stock. For paragraph (3), the constructive-ownership rules in section 1563(e) of title 26, other than paragraph (3)(C), apply, including those rules as applied through section 414(c) of title 26.