38 CFR § 20.300 — Rule 300. General

(a) Decisions of the Board will be based on a de novo review of the evidence of record at the time of the agency of original jurisdiction decision on the issue or issues on appeal, and any additional evidence or testimony submitted pursuant to this subpart, as provided in § 20.801.

(b) Waiver of appellant's right to submit evidence. For appeals described in 20.302 and 20.303, an appellant has a right to submit evidence during a period of 90 days, unless this right is waived by the appellant or representative at any time prior to the expiration of the applicable 90-day period. Such a waiver must be in writing or, if a hearing on appeal is conducted pursuant to 20.302, the waiver must be formally and clearly entered on the record orally at the time of the hearing.