29 CFR 4000.1 - What are these filing rules about?
Where a particular regulation calls for their application, the rules in this subpart A of part 4000 tell you what filing methods you may use for any submission (including a payment) to us. They do not cover an issuance from you to anyone other than the PBGC, such as a notice to participants. Also, they do not cover filings with us that are not made under our regulations, such as procurement filings, litigation filings, and applications for employment with us. (Subpart B tells you what methods you may use to issue a notice or otherwise provide information to any person other than us. Subpart C tells you how we determine your filing or issuance date. Subpart D tells you how to compute various periods of time. Subpart E tells you how to maintain required records in electronic form.)