Medical evidence is the clinical record of a condition: service treatment records, VA medical records, private treatment records, hospital reports, and examination findings. The VA also accepts supporting statements from people who know the veteran, but those are lay evidence, a different category. The clinical record carries the diagnostic weight.

The practical rule underneath the whole system is simple to state. The VA rates what is documented. A condition that is real but absent from the record cannot support a rating, and a condition documented vaguely tends to be rated as though it were mild. Evidence quality is the substance of the decision.

A service-connected disability claim rests on three elements. First, a current diagnosed condition, stated in the record by a qualified clinician. Second, documented severity: how the condition actually limits work, sleep, and daily activity, in terms concrete enough to rate. Third, a connection to service: the link between the condition and the veteran's time in uniform.

The three elements divide cleanly between professions. Medical professionals establish the diagnosed condition and document its severity; that is clinical work. The connection to service is argued to the VA as part of the claim itself, which is the work of a VA-accredited representative or a Veterans Service Organization. Understanding which element belongs to whom explains most of how the claims ecosystem is organized.

The VA's Schedule for Rating Disabilities, published at 38 CFR Part 4, assigns percentage ratings against specific documented criteria. For most conditions the difference between adjacent ratings is a difference in documented severity: range of motion measured in degrees, frequency of episodes, the specific functional limits a clinician recorded.

This is why two veterans with the same condition can receive different ratings. The rating reflects the record, and records differ. A clinician who documents functional impact in measurable terms gives the rating schedule something to work with. A record that says a condition exists, without saying what it prevents, leaves the severity question open, and open questions tend to resolve conservatively.

A complete record states each diagnosis explicitly, coded to the specificity the clinical evidence supports, using the ICD-10 classification that United States healthcare runs on. It documents severity in functional terms: what the condition does to work, sleep, concentration, and daily activity. It shows treatment history and consistency over time, because a condition documented once in a decade reads differently than one documented across regular care.

Organization matters more than most people expect. VA reviewers work through large files. A record that is legible, complete, and internally consistent gets evaluated on its content. A record with gaps and contradictions generates development letters, examinations, and delay.

When the VA needs more medical information to decide a claim, it schedules a claim exam, commonly called a C&P exam, performed by a VA or VA-contracted examiner at no cost to the veteran. The examiner reviews the file, examines the veteran, and completes standardized findings the rating activity uses.

The C&P exam supplements the record; it does not replace it. An examiner with a thorough file in front of them is confirming documented findings. An examiner with a thin file is producing much of the evidence in a single visit. Veterans are also free to submit private medical evidence, including evaluations from their own clinicians, and the VA is required to consider it.

Clinicians diagnose, treat, and document; their independent judgment is what gives medical evidence its weight. Accredited representatives and Veterans Service Organizations prepare, present, and prosecute the claim; federal law restricts that work to individuals and organizations accredited by the VA's Office of General Counsel, and VSO help is free. The veteran owns the middle: their records, their choice of representative, and the decision to file at all.

Every role in the system can be checked. The VA publishes its accreditation database, its rating schedule, and its claim exam process. The sources below are the primary references this article draws on.