38 C.F.R. § 36.4335
Except where otherwise specified in this part, any notice required by §§ 36.4300 to 36.4380 to be given the Secretary must be in writing or such other communications medium as may be approved by an official designated in § 36.4345 and delivered, by mail or otherwise, to the VA office at which the guaranty or insurance was issued, or to any changed address of which the holder has been given notice. Such notice must plainly identify the case by setting forth the name of the original veteran-obligor and the file number assigned to the case by the Secretary, if available, or otherwise the name and serial number of the veteran. If mailed, the notice shall be by certified mail when so provided by §§ 36.4800 to 36.4880 .
38 C.F.R. §36.4335
Authority: 38 U.S.C. 3703(c)(1)