29 C.F.R. § 4003.22

(a) General rule. Except as provided in paragraph (b) of this section, an initial determination covered by this subpart will not become effective until the prescribed period of time for filing a request for reconsideration under subpart C of this part or an appeal under subpart D of this part, whichever is applicable, has elapsed. The filing of a request for review under subpart C or D of this part will automatically stay the effectiveness of an initial determination until a decision on the request for review has been issued by PBGC.

(b) Exception. Except for initial determinations listed in § 4003.1(e)(2), (3), and (6), PBGC may, in its discretion, order that the initial determination in a case is effective on the date it is issued. When PBGC makes such an order, the initial determination will state that it constitutes the final agency action effective on the date of issuance, there is no right to request review under subparts C and D of this part, and any person aggrieved by the initial determination has exhausted all administrative remedies.