29 C.F.R. § 4043.4 – Waivers and extensions.

(a) Waivers and extensions—in general. PBGC may extend any deadline or waive any other requirement under this part where it finds convincing evidence that the waiver or extension is appropriate under the circumstances. Any waiver or extension may be subject to conditions. A request for a waiver or extension must be filed with PBGC in writing (which may be in electronic form) and must state the facts and circumstances on which the request is based.
(b) Waivers and extensions—specific events. For some reportable events, automatic waivers from reporting and extensions of time are provided in subparts B and C of this part. If an occurrence constitutes two or more reportable events, reporting requirements for each event are determined independently. For example, reporting is automatically waived for an occurrence that constitutes a reportable event under more than one section only if the requirements for an automatic waiver under each section are satisfied.
(c) Multiemployer plans. The requirements of section 4043 of ERISA are waived with respect to multiemployer plans.
(d) Terminating plans. No notice is required from the plan administrator or contributing sponsor of a plan if the notice date is on or after the date on which—
1. (1) All of the plan's assets (other than any excess assets) are distributed pursuant to a termination under part 4041 of this chapter; or
2. (2) A trustee is appointed for the plan under section 4042 of ERISA.
(e) Events not described in this part. Notice of a reportable event described in section 4043(c) of ERISA is waived except to the extent that reporting is required under this part.