Key Takeaways
A nexus letter is a written medical opinion connecting a current condition to an in-service event, injury, or exposure, and it is often the single factor that decides a VA disability claim that is not automatically presumed to be service-connected. The letter must use the VA's exact legal standard — that the condition is “at least as likely as not” related to service — and a letter from the wrong provider, or one that uses softer language, can sink an otherwise strong claim. Sean Kendall's legal team works with a network of independent medical experts to build nexus opinions that hold up under VA review, and to challenge negative opinions issued by VA examiners.
Every VA disability claim comes down to proving three things: a current diagnosis, an event or exposure that happened during military service, and a documented link between the two. Veterans usually have no trouble with the first two. It is the third piece — the medical nexus — where claims are won or lost, and it is also the piece most Veterans have never heard of until the VA denies their claim. If you are trying to determine whether your claim needs a nexus letter or whether the one you already have is strong enough, contact Sean Kendall's legal team before submitting anything further to the VA.
What Is a Nexus Letter?
A nexus letter, sometimes called an Independent Medical Opinion, is a written statement from a licensed medical provider that explains the relationship between a Veteran's current condition and their time in service. To satisfy the VA, the letter has to say more than "this could be related." It must state that the condition is "at least as likely as not" caused or aggravated by an in-service event. That phrase reflects the VA's reasonable-doubt standard under 38 CFR § 3.102, which requires the VA to resolve close calls in the Veteran's favor rather than the claimant's.
Does Every VA Claim Need a Nexus Letter?
Not always. Some conditions qualify for presumptive service connection, meaning the VA already accepts that the condition is connected to certain types of service without requiring the Veteran to prove it individually. For every other claim, a nexus letter is usually the only way to satisfy the third pillar.
Direct Service Connection Claims
In a direct claim, the nexus letter must tie a specific in-service event — an injury, an illness, or a documented incident — to the condition the Veteran has today. This is common in claims for PTSD and traumatic brain injury, where the connection between the event and the diagnosis is not always obvious from the records alone.
Secondary Service Connection Claims
A secondary claim argues that one already-service-connected condition caused or worsened a second condition. Here, the nexus letter must explain the medical mechanism linking the two—for example, how a service-connected orthopedic injury led to a gait change that damaged another joint. Secondary claims often fail not because the connection is untrue, but because the letter never explains how one condition led to the other.
What Makes a Nexus Letter Strong Enough to Win?
Not all nexus letters carry the same weight with the VA. The role independent medical experts play in writing an effective nexus letter comes down to a handful of elements that separate a persuasive opinion from one the VA can dismiss:
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The author's credentials — a licensed physician, ideally one who treats the specific condition at issue
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A documented review of the Veteran's service records and medical history, not just a brief office note
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The correct legal language — "at least as likely as not," rather than weaker phrasing like "possibly" or "could be"
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A clear medical rationale that connects the specific service history to the current diagnosis
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An acknowledgment of alternative causes, and an explanation of why the in-service event is still the more likely one
Who Is Allowed to Write a Nexus Letter?
VA doctors cannot write nexus letters for a Veteran's own claim, since they are not considered independent. The letter has to come from a private provider — a physician and, in some claim types, a psychologist or psychiatrist — who has no financial or institutional stake in the VA's decision. Finding the right specialist for a specific condition, particularly an uncommon one, is often the hardest part of the process for a Veteran to manage on their own.
What Happens if a VA Examiner Disagrees With Your Nexus Letter?
The VA frequently schedules its own Compensation & Pension exam, and the examiner's opinion does not always match a Veteran's private nexus letter. When that happens, the case often comes down to which opinion is better reasoned, not which one came first. Under 38 U.S.C. § 5107(b), the VA must resolve the claim in the Veteran's favor whenever the evidence on both sides is in approximate balance. A well-supported private nexus letter can outweigh an unexplained or conclusory VA opinion, which is why Veterans facing a negative C&P finding often still have a path forward through a supplemental claim or an appeal to the Court of Appeals for Veterans Claims.
How Sean Kendall's Legal Team Builds a Strong Nexus Opinion
Obtaining a nexus letter is not just a matter of finding a willing doctor. Sean Kendall's legal team works with a network of independent medical experts across a wide range of specialties, which means a Veteran's claim can be matched with a provider who has real experience with the specific condition at issue — whether that is a physical injury, a case pursuing TDIU benefits, or something harder to source. Our team gathers and organizes the service and medical records the expert needs, briefs the provider on the VA's legal standard so the letter uses the correct language from the start, and reviews the draft before submission.
A nexus letter can win or lose a VA claim. If your claim is missing a nexus letter or if the VA has already issued a decision that relied on a weak or unfavorable medical opinion, Sean Kendall's legal team can help you build the evidence your case needs.