A buddy statement is a written statement from someone who has personal knowledge of your military service, in-service events, or current symptoms. The VA accepts lay evidence — statements from non-medical witnesses — as competent evidence for facts that do not require medical expertise. A fellow service member can describe the noise environment in your unit. A spouse can describe your nightmares and behavioral changes. A coworker can describe how your condition affects your job performance.
Buddy statements are submitted on VA Form 21-4138 (Statement in Support of Claim) or as a plain letter. The statement should include the writer's full name, relationship to the veteran, how they know the facts they are describing, specific observations (not conclusions), and approximate dates.
Effective buddy statements are specific and observational. "John has bad knees" is weak. "I served with John in the 3rd Battalion from 2008 to 2010. During our deployment to Afghanistan, I personally witnessed him injure his right knee during a dismounted patrol on approximately March 15, 2009, when he fell while carrying a full combat load over rough terrain. After that incident, he regularly complained of knee pain and I observed him limping, particularly after long patrols" is strong because it provides who, what, when, where, and personal observation.
For current symptoms, buddy statements from family members are particularly powerful. A spouse's statement describing sleep disturbances, mood changes, social withdrawal, or physical limitations provides an outside perspective that corroborates the veteran's own account.
The VA is required to consider competent lay evidence. If your claim is denied and the decision does not address submitted buddy statements, that can be a basis for appeal.