38 C.F.R. § 19.53
An extension of the 60-day period for filing a Substantive Appeal, or the 30-day period for responding to a Supplemental Statement of the Case, may be granted for good cause. A request for such an extension must be in writing and must be made prior to expiration of the time limit for filing the Substantive Appeal or the response to the Supplemental Statement of the Case. The request for extension must be filed with the Department of Veterans Affairs office from which the claimant received notice of the determination being appealed, unless notice has been received that the applicable records have been transferred to another Department of Veterans Affairs office. A denial of a request for extension may be appealed to the Board.
38 C.F.R. §19.53
Authority: 38 U.S.C. 7105(d)(3) (2016)