VA Claim Evidence Guide
Nexus Letter for VA Disability Claims
A nexus letter is often the single most important piece of evidence in a VA disability claim. It is a medical opinion that connects a veteran's current diagnosis to an event, injury, or exposure during military service. Without a credible nexus, most claims are denied for lack of service connection.
The four required elements
A current, diagnosed condition
The letter must identify a specific diagnosis the veteran has today (e.g., lumbar degenerative disc disease, PTSD, sleep apnea). Vague symptoms are not enough.
An in-service event, injury, or exposure
The provider should reference the documented in-service event — a specific injury, stressor, hazardous exposure, or repetitive activity — pulled from service treatment records or personnel records.
A medical opinion linking the two
The provider gives a probability opinion. VA looks for the phrase 'at least as likely as not' (50% or greater) that the current condition is caused by, or aggravated by, service.
A clear rationale
The opinion is only as strong as its reasoning. The provider should cite medical literature, exam findings, records reviewed, and their clinical experience — not just conclusions.
The "at least as likely as not" standard
VA uses a 50%-or-greater probability threshold. If the medical evidence is in equipoise — meaning the odds it is service-connected are 50/50 — the tie goes to the veteran under 38 CFR § 3.102 (benefit of the doubt). That is why "at least as likely as not" is the magic phrase: it puts the opinion right at the threshold VA is required to accept.
Nexus letter checklist
- Provider's full name, credentials, license number, and specialty
- Statement that the veteran's records were reviewed (list what was reviewed)
- Current diagnosis with ICD-10 code when possible
- Reference to the in-service event with dates
- The 'at least as likely as not' opinion language
- Detailed medical rationale citing findings and literature
- Signature and date
Common mistakes that sink nexus letters
- Using speculative language like 'could be related' — VA reads this as less than 50%.
- No rationale, just a conclusion. A one-line letter almost always loses on appeal.
- Provider never reviewed the C-file or service treatment records.
- Missing the secondary-service-connection framing when the claim is secondary (e.g., depression secondary to chronic pain).
How StratForge helps you prepare
StratForge Veterans AI organizes your VA records, extracts the in-service events and current diagnoses your provider will need to reference, and helps you build a clear evidence packet before you request a nexus opinion. Providers write stronger letters when the timeline and records are already assembled.
Educational information only. StratForge Group LLC is not a law firm, accredited VSO, or medical provider, and does not represent veterans before the VA.