29 C.F.R. § 4062.5

(a) General. Unless the PBGC establishes an earlier net worth record date pursuant to paragraph (b) of this section, the net worth record date, for all purposes under this part, is the plan's termination date.

(b) Establishment of an earlier net worth record date. At any time during a termination proceeding, the PBGC, in order to prevent undue loss to or abuse of the plan termination insurance system, may establish as the net worth record date an earlier date during the 120-day period ending with the termination date.

(c) Notification. Whenever the PBGC establishes an earlier net worth record date, it shall immediately give liable person(s) written notification of that fact. The written notice may also include a request for additional information, as provided in § 4062.6(a)(3).