49 CFR § 31.47
Limitations
November 18, 2020
(a) The notice of hearing with respect to a claim or statement must be served in the manner specified in §31.8 within 6 years after the date on which such claim or statement is made.
(b) If the defendant fails to serve a timely answer, service of a notice under §31.10(b) shall be deemed a notice of hearing for purposes of this section.
(c) The statute of limitations may be extended by agreement of the parties.