26 C.F.R. § 1.410(b)-9
In applying this section and §§ 1.410(b)-2 through 1.410(b)-10 , the definitions in this section govern unless otherwise provided.
Collectively bargained employee. Collectively bargained employee means a collectively bargained employee within the meaning of § 1.410(b)-6(d)(2) .
Defined benefit plan. Defined benefit plan means a defined benefit plan within the meaning of section 414(j). The portion of a plan described in section 414(k) that does not consist of separate accounts is treated as a defined benefit plan.
Defined contribution plan. Defined contribution plan means a defined contribution plan within the meaning of section 414(i). The portion of a plan described in section 414(k) that consists of separate accounts is treated as a defined contribution plan.
Employee. Employee means an individual who performs services for the employer who is either a common law employee of the employer, a self-employed individual who is treated as an employee pursuant to section 401(c)(1), or a leased employee (not excluded under section 414(n)(5)) who is treated as an employee of the employer-recipient under section 414(n)(2) or 414(o)(2). Individuals that an employer treats as employees under section 414(n) pursuant to the requirements of section 414(o) are considered to be leased employees for purposes of this rule. In addition, an individual must be treated as an employee with respect to allocations under a defined contribution plan taken into account under § 1.401(a)(4) -2(c)(ii) and with respect to increases in accrued benefits (within the meaning of 411(a)(7)) under a defined benefit plan that are based on ongoing service or compensation (including imputed service or compensation) credits.
Employer. Employer means the employer maintaining the plan and those employers required to be aggregated with the employer under sections 414(b), (c), (m), or (o). An individual who owns the entire interest of an unincorporated trade or business is treated as an employer. Also, a partnership is treated as the employer of each partner and each employee of the partnership.
ESOP. ESOP or employee stock ownership plan means an employee stock ownership plan within the meaning of section 4975(e)(7) or a tax credit employee stock ownership plan within the meaning of section 409(a).
Former employee. Former employee means an individual who was, but has ceased to be, an employee of the employer (i.e., the individual has ceased performing services as an employee for the employer). An individual is treated as a former employee beginning on the day after the day on which the individual ceases performing services as an employee for the employer. Thus, an individual who ceases performing services as an employee for an employer during a plan year is both an employee and a former employee for the plan year. Notwithstanding the foregoing, an individual is an employee (and not a former employee) to the extent that the individual is treated as an employee with respect to the plan for the plan year under the definition of employee in this section.
Highly compensated employee. Highly compensated employee means an employee who is a highly compensated employee within the meaning of section 414(q) or a former employee treated as an employee under the definition of employee in this section who is a highly compensated former employee within the meaning of section 414(q).
Highly compensated former employee. Highly compensated former employee means a former employee who is a highly compensated former employee within the meaning of section 414(q).
Multiemployer plan. Multiemployer plan means a multiemployer plan within the meaning of section 414(f).
Noncollectively bargained employee. Noncollectively bargained employee means an employee who is not a collectively bargained employee.
Nonhighly compensated employee. Nonhighly compensated employee means an employee who is not a highly compensated employee.
Nonhighly compensated former employee. Nonhighly compensated former employee means a former employee who is not a highly compensated former employee.
Plan year. Plan year means the plan year of the plan as defined in the written plan document. In the absence of a specifically designated plan year, the plan year is deemed to be the calendar year.
Plan year compensation. Plan year compensation means plan year compensation within the meaning of § 1.401(a)(4) -12.
Professional employee. Professional employee means any highly compensated employee who, on any day of the plan year, performs professional services for the employer as an actuary, architect, attorney, chiropodist, chiropractor, dentist, executive, investment banker, medical doctor, optometrist, osteopath, podiatrist, psychologist, certified or other public accountant, stockbroker, or veterinarian, or in any other professional capacity determined by the Commissioner in a notice or other document of general applicability to constitute the performance of services as a professional.
Ratio percentage. With respect to a plan for a plan year, a plan's ratio percentage means the percentage (rounded to the nearest hundredth of a percentage point) determined by dividing the percentage of the nonhighly compensated employees who benefit under the plan by the percentage of the highly compensated employees who benefit under the plan. The percentage of the nonhighly compensated employees who benefit under the plan is determined by dividing the number of nonhighly compensated employees benefiting under the plan by the total number of nonhighly compensated employees of the employer. The percentage of the highly compensated employees who benefit under the plan is determined by dividing the number of highly compensated employees benefiting under the plan by the total number of highly compensated employees of the employer.
Section 401(k) plan. Section 401(k) plan means a plan consisting of elective contributions described in § 1.40(k)-1(g)(3) under a qualified cash or deferred arrangement described in § 1.401(k)-1(a)(4)(i) . Thus, a section 401(k) plan does not include a plan (or portion of a plan) that consists of contributions under a nonqualified cash or deferred arrangement, or qualified nonelective or qualified matching contributions treated as elective contributions under § 1.401(k)-1(a)(6) .
Section 401 (l) plan. Section 401 (l) plan means a plan that-
Section 401(m) plan. Section 401(m) plan means a plan consisting of employee contributions described in § 1.401(m)-1(f)(6) or matching contributions described in § 1.40(m)-1(f)(12) , or both. Thus, a section 401(m) plan does not include a plan (or portion of a plan) that consists of elective contributions or qualified nonelective contributions treated as matching contributions under § 1.401(m)-1(b)(5) .
26 C.F.R. §1.410(b)-9