The single most important document in most claims. Magic language: "at least as likely as not [condition] was caused by [event]." Anything less specific risks denial. Have your private doctor write it; use the generator to draft.
📑 On this page
The nexus letter — magic language that wins
Key concept. The nexus letter is the single most important document in most claims. It is a written opinion from a medical professional connecting your current condition to your service or to another service-connected condition. VA raters look for specific phrases. Get the phrases right, win the claim. Get them wrong, lose the claim.
Who can write a nexus letter
- Any licensed physician (MD or DO)
- Licensed nurse practitioners and physician assistants (with some limits on mental health diagnoses)
- Licensed clinical psychologists and psychiatrists (essential for mental health claims)
- Audiologists (for hearing loss and tinnitus)
- Specialists in the relevant field (orthopedist for joints, pulmonologist for respiratory, etc.) carry the most weight
The three standards of probability — get the wording right
| Phrase | Meaning | Does it win? |
|---|---|---|
| ”At least as likely as not…“ | 50% or higher probability | YES — this is the threshold for service connection |
| ”More likely than not…” | Greater than 50% | YES — even stronger than the minimum |
| ”Less likely than not…” | Less than 50% | NO — fails the standard |
If a doctor writes “likely caused by” or “possibly related to,” the rater may interpret that ambiguously. Get them to use the precise statutory language: “at least as likely as not.”
What a strong nexus letter contains
- Identification of the doctor, credentials, and basis for opinion (review of records, examination).
- Statement of the current diagnosis with ICD-10 code if possible.
- Reference to the relevant in-service event or service-connected primary condition.
- The opinion sentence: “It is at least as likely as not that [the veteran’s condition] was caused by [OR aggravated beyond its natural progression by] [in-service event or service-connected condition].”
- The rationale — WHY the doctor reached that conclusion. Cite medical literature when possible. The rationale is what makes the opinion withstand a contradictory C&P exam.
- Signature, date, and credentials.
Pro tip
If your private doctor is unsure how to write a nexus letter, you have two options: (1) pay for an Independent Medical Opinion (IMO) from a veteran-focused medical-legal provider — typical cost $500–$2,500, often pays for itself many times over in awarded benefits, or (2) use the nexus letter generator to draft the letter for the doctor and provide them the CFR language they need. Many doctors will sign a well-drafted letter once you make their job easy.
Other resources — tools · conditions · how to file · forms · FAQ