20 C.F.R. § 261.1 : Employees' Benefits — RAILROAD RETIREMENT BOARD — REGULATIONS UNDER THE RAILROAD RETIREMENT ACT — ADMINISTRATIVE FINALITY — Reopening and revising decisions

(a) This part sets forth the Board's rules governing finality of decisions. After the expiration of the time limits for review as set forth in part 260 of this chapter, decisions of the agency may be reopened and revised under the conditions described in this part, by the bureau, office, or entity that made the earlier decision or by a bureau, office, or other entity at a higher level, which has the claim properly before it.
(b) A final decision as that term is used in this part means any decision of the type listed in §260.1 of this chapter where the time limits for review as set forth in part 260 of this chapter or in the Railroad Retirement Act have expired.
(c) Reopening a final decision under this part means a conscious determination on the part of the agency to reconsider an otherwise final decision for purposes of revising that decision.
(d) New and material evidence as that phrase is used in this part means evidence that may reasonably be expected to affect a final decision, which was unavailable to the agency at the time the decision was made, and which the claimant could not reasonably have been expected to have submitted at that time.

20 C.F.R. § 261.1