; or (B) a church or a convention or association of churches that is exempt from tax under section 501 of such Code. (5) Aggregation rule A person treated as a single employer under subsection (a) or (b) of section 52 of the Internal Revenue Code of 1986 or subsection (m) or (o) of section 414 of such Code shall be treated as a single employer. (c) Qualifying employee For purposes of this title— (1) In general The term qualifying employee means any employee who is not an excluded employee. (2) Plan sponsor's employees If— (A) an employer maintains one or more qualifying plans or arrangements described in section 219(g)(5) of the Internal Revenue Code of 1986; and (B) the employees of a subsidiary, division, or other business unit are generally not eligible to participate in any such qualifying plan or arrangement, for purposes of this section, the employer shall be treated as a covered employer with respect to such employees (other than excluded employees), and such employees (other than excluded employees) shall be treated as qualifying employees for the calendar year. (3) Excluded employees (A) In general The term excluded employee means an employee who is an excludable employee and who is in a class or category that the employer excludes from treatment as qualifying employees. (B) Excludable employee The term excludable employee means— (i) an employee described in section 410(b)(3) of the Internal Revenue Code of 1986; (ii) an employee who has not attained the age of 21 before the beginning of the calendar year; (iii) an employee who has not completed at least 3 months of service with the employer; (iv) in the case of an employer that maintains a qualifying plan or arrangement which excludes employees who have not satisfied the minimum age and service requirements for participation in the plan, an employee who has not satisfied such requirements