long-term, part-time workers For purposes of paragraph (2)(D)(ii)— (A) Age requirement must be met Paragraph (2)(D)(ii) shall not apply to an employee unless the employee has met the requirement of section 410(a)(1)(A)(i) by the close of the last of the 12-month periods described in such paragraph. (B) Nondiscrimination and top-heavy rules not to apply (i) Nondiscrimination rules In the case of employees who are eligible to participate in the arrangement solely by reason of paragraph (2)(D)(ii)— (I) notwithstanding subsection (a)(4), an employer shall not be required to make nonelective or matching contributions on behalf of such employees even if such contributions are made on behalf of other employees eligible to participate in the arrangement, and (II) an employer may elect to exclude such employees from the application of subsection (a)(4), paragraphs (3), (12), and (13), subsection (m)(2), and section 410(b). (ii) Top-heavy rules An employer may elect to exclude all employees who are eligible to participate in a plan maintained by the employer solely by reason of paragraph (2)(D)(ii) from the application of the vesting and benefit requirements under subsections (b) and (c) of section 416. (iii) Vesting For purposes of determining whether an employee described in clause (i) has a nonforfeitable right to employer contributions (other than contributions described in paragraph (3)(D)(i)) under the arrangement, each 12-month period for which the employee has at least 500 hours of service shall be treated as a year of service. (iv) Employees who become full-time employees This subparagraph shall cease to apply to any employee as of the first plan year beginning after the plan year in which the employee meets the requirements of section 410(a)(1)(A)(ii) without regard to paragraph (2)(D)(ii). (C) Exception for employees under collectively bargained plans, etc Paragraph (2)(D)(ii) shall not apply to employees described in section 410(b)(3). (D) Special rules (i) Time of participation The rules of section 410(a)(4)