29 C.F.R. § 4000.31
Is my issuance untimely if I miss a few participants or beneficiaries?
eCFR editorial change effective 2017-01-01 · current text
The PBGC will not treat your issuance as untimely based on your failure to provide the issuance to a participant or beneficiary in a timely manner if—
(a) The failure resulted from administrative error;
(b) The failure involved only a de minimis percentage of intended recipients; and
(c) You resend the issuance to the intended recipient promptly after discovering the error.