1. (a) The following terms are defined in § 4001.2 of this chapter: employer, ERISA, IRS, mass withdrawal, multiemployer plan, nonforfeitable benefit, PBGC, plan, and plan year.

2. (b) For purposes of this part:

   Initial withdrawal liability means the amount of withdrawal liability determined in accordance with sections 4201 through 4225 of title IV without regard to the occurrence of a mass withdrawal.

   Mass withdrawal liability means the sum of an employer's liability for de minimis amounts, liability for 20-year-limitation amounts, and reallocation liability.

   Mass withdrawal valuation date means—

   1. (1) In the case of a termination by mass withdrawal, the last day of the plan year in which the plan terminates; or
   2. (2) in the case of a withdrawal of substantially all employers pursuant to an agreement or arrangement to withdraw, the last day of the plan year as of which substantially all employers have withdrawn.

   Reallocation liability means the amount of unfunded vested benefits allocated to an employer in the event of a mass withdrawal.

   Reallocation record date means a date selected by the plan sponsor, which is not earlier than the date of the plan's actuarial report for the year of the mass withdrawal and not later than one year after the mass withdrawal valuation date.

   Redetermination liability means the sum of an employer's liability for de minimis amounts and the employer's liability for 20-year-limitation amounts.

   Unfunded vested benefits means the amount by which the present value of a plan's nonforfeitable benefits exceeds the value of plan assets (including claims of the plan for unpaid initial withdrawal liability and redetermination liability), determined in accordance with section 4281 of ERISA and part 4281, subpart B.

3. (c) For purposes of subpart B—

   Withdrawal means a complete withdrawal as defined in section 4203 of ERISA.

[61 FR 34102, July 1, 1996, as amended at 73 FR 79636, Dec. 30, 2008; 86 FR 1277, Jan. 8, 2021]