38 CFR 21.31: Informal claim.

Any communication or action indicating an intent to apply for rehabilitation or employment assistance, from a veteran, a duly authorized representative, or a Member of Congress may be considered an informal claim. Upon receipt of an informal claim, if a formal claim has not been filed, an application form will be forwarded to the veteran for execution. In the case of a claim for rehabilitation, or employment assistance, the formal claim will be considered filed as of the date of receipt of the informal claim if received within 1 year from the date it was sent to the veteran, or before cessation of the course, whichever is earlier.