34 C.F.R. § 370.16
(d) The Secretary sends copies of the decision to the parties by registered or certified mail, return receipt requested, or other means that provide a record of receipt by both parties.
(Approved by the Office of Management and Budget under control number 1820-0520)
(Authority: Sections 12(c) and 112(c)(1)(B) of the Rehabilitation Act of 1973, as amended; 29 U.S.C. 709(c) and 732(c)(1)(B))