(a) General rule. An employer that withdraws in a plan year in which substantially all employers withdraw from the plan shall be liable to the plan for de minimis amounts if the employer's initial withdrawal liability was reduced pursuant to section 4209(a) or (b) of ERISA.

(b) Amount of liability. An employer's liability for de minimis amounts under this section shall be determined pursuant to § 4219.13.

(c) Plan sponsor's obligations. The plan sponsor of a plan that experiences a withdrawal described in paragraph (a) shall—

(1) Determine and collect initial withdrawal liability of every employer that has completely or partially withdrawn, in accordance with sections 4201 and 4202 of ERISA;

(2) Notify each employer that is or may be liable under this section, in accordance with paragraph (d) of this section;

(3) Within 90 days after the end of the plan year in which the withdrawal occurred, determine, in accordance with paragraph (b) of this section, the liability of each withdrawing employer that is liable under this section;

(4) Notify each liable employer, in accordance with paragraph (e) of this section, of the amount of its liability under this section, demand payment of and collect that liability; and

(5) Certify to the PBGC that determinations of liability have been completed, in accordance with paragraph (g) of this section.

(d) Notice of withdrawal. Within 30 days after the end of a plan year in which a plan experiences a withdrawal described in paragraph (a), the plan sponsor shall notify in writing each employer that is or may be liable under this section. The notice shall specify the plan year in which substantially all employers have withdrawn, describe the consequences of such withdrawal under this section, and state that an employer obligated to make initial withdrawal liability payments shall continue to make those payments in accordance with its schedule.

(e) Notice of liability. Within 30 days after the determination of liability, the plan sponsor shall issue a notice of liability in writing to each liable employer. The notice shall include—

(1) The amount of the employer's liability for de minimis amounts;

(2) A schedule for payment of the liability, determined under § 4219.16(f); and

(3) A demand for payment of the liability in accordance with the schedule.

(f) Review of liability determinations. Determinations of liability made pursuant to this section shall be subject to plan review under section 4219(b)(2) of ERISA and to arbitration under section 4221 of ERISA, subject to the limitations contained in § 4219.16(g).

(g) Notice to the PBGC. No later than 30 days after the notices of liability under this section are required to be provided to liable employers, the plan sponsor shall file with the PBGC a notice. The notice shall include the items described in § 4219.17 (g)(1) through (g)(3), as well as the information listed below. In addition, the PBGC may require the plan sponsor to submit any further information that the PBGC determines it needs in order to monitor compliance with this section.

(1) The plan year in which the withdrawal occurred.

(2) A description of the effect of the withdrawal, including the number of contributing employers that withdrew in the plan year in which substantially all employers withdrew, the number of employers remaining in the plan, and a description of the effect of the withdrawal on the plan's contribution base.

(3) A certification, signed by the plan sponsor or duly authorized representative, that determinations have been made and notices given in accordance with this section.