Start here
Change the word you use
"Nexus letter" is claim-world slang. It is not a VA term.
- Nexus just means the link — the connection between your current condition and
something that happened in service.
- When you talk to a doctor or a clinic, ask for a medical opinion on causation. That is
language a clinician recognizes and can act on.
- Ask for it to be written in VA's own standard: is this condition at least as likely as
not related to service.
- Three things make a service-connection claim: a current disability, an
in-service event, injury or illness, and a link between the two. The opinion is
the third piece only.
Say it exactly like this at the desk: "I am filing a VA disability claim. I am asking for a
medical opinion on whether my condition is at least as likely as not related to my military
service."
✅ Ask for a medical opinion, not a letter.
The standard
The bar is 50/50, not proof
This is the single most expensive thing veterans do not know.
- You do not have to prove your case beyond doubt. You have to get the evidence to an
approximate balance.
- Under 38 CFR 3.102, when
the positive and negative evidence on a point are in approximate balance, reasonable doubt is
resolved in your favor.
- That is why the standard wording is "at least as likely as not" — 50 percent or
greater. Not "definitely." Not "caused by."
- A doctor who will not write "caused by" may still be willing to write "at least as likely as
not." Those are not the same question. Ask the second one.
A tie goes to you. Anybody telling you that you have to be certain, or that your doctor has to
be certain, is telling you the bar is higher than the regulation sets it.
✅ A tie is a win. Say the words.
What makes it strong
Reasoning, not letterhead
A signature with nothing behind it does very little for you.
- VHA policy requires a provider who states causality to include a clear and specific
rationale citing the evidence. That rationale is the point of the document.
- The opinion should rest on an accurate and complete factual history — your service
records, your treatment records, your timeline. An opinion built on a wrong history is easy to
set aside.
- It should name the condition, name the in-service event or exposure, and state the
likelihood in VA's language.
- Boilerplate that never mentions your actual records is weak no matter who signed it.
Stronger, but not required: addressing other plausible causes, and answering a negative
C&P exam point by point. No regulation requires either one. Do not hold your claim back
because your opinion does not do both — file it.
✅ The "why" is the whole document.
Free route 1
VA has to go get it — at its own cost
This route is open to every claimant, enrolled in VA health care or not.
- Under 38 CFR 3.159(c)(4),
VA must provide a medical examination or obtain a medical opinion when the record shows all
three of:
- 1 competent lay or medical evidence of a current diagnosed
disability, or persistent or recurrent symptoms of a disability;
- 2 evidence that an event, injury or disease occurred in
service;
- 3 an indication that the disability or symptoms may be
associated with that service.
- VA's own words on its duty to assist: "we may also ask you to have a claim exam (also called
a C&P exam). Or we may request a medical opinion."
VA does not charge you for the opinion it obtains itself. That threshold is low on
purpose — an "indication" is not proof. Lay evidence counts toward it. So does your own
statement of symptoms.
Ask in writing, in your claim or in a statement, that VA obtain a medical opinion under its duty
to assist, and say which condition and which in-service event you are tying together. Keep a
copy. See
va.gov/resources/vas-duty-to-assist.
✅ Make VA do its job first.
Free route 2
Your VA provider — what they can and cannot do
Permitted. Discretionary. Not guaranteed. Know this before you walk in.
- The policy is VHA Directive 1134(3), "Provision of Medical Statements and Completion
of Forms by VA Health Care Providers," originally dated 28 November 2016 and amended 8 July
2025. Name it by number and by that amendment —
read it here.
- It requires VA providers to assist patients with completing forms and providing medical
statements, and it addresses providers who wish to provide medical opinions that state
causality.
- It also says service connection and disability ratings are purely legal determinations
belonging exclusively to the Veterans Benefits Administration, and that VA providers are
often not well suited to assess causality of a current condition in a way that helps VBA
adjudicate.
- So a causation opinion is the clinician's discretion, not your entitlement. If your
provider declines, that refusal is lawful. Do not go to war with them over it.
- This route also requires that you are enrolled in VA health care with an established VA
provider. The VA medical benefits package at
38 CFR 17.38 is a benefit for
enrolled and eligible veterans. No enrollment, no VA provider route.
If you are told no: you are not out of options. Route 1 above still stands — VA's duty to
assist does not depend on your provider's willingness. A private provider is the other door. Ask
for your records either way.
✅ Ask politely. Have a plan B.
Free route 3
Your own doctor, VA's own forms
A provider you already see may be able to do this at no extra charge.
- VA publishes Disability Benefits Questionnaires (DBQs) organized by body system, and a
private provider may complete them —
public DBQs on VA.gov.
- Some DBQs are not available for public use because of limits in federal regulation or
specialized training needed to complete them. The list tells you which.
- A form helps. Boilerplate does not. VA weighs the rationale and whether it fits your actual
record.
- Let VA collect your private treatment records for free: VA Form 21-4142 and
21-4142a authorize VA to request records from your non-VA providers.
Many primary care providers will complete a form during a normal appointment. You will never
know until you ask. Bring the DBQ printed and bring your timeline.
✅ Ask the doctor you already have.
Do not do this
Do not write it and ask them to sign
You have probably seen this advice online. It can cost you the opinion.
- You may hand your provider the relevant records, a written timeline, and the standard
wording VA uses — "at least as likely as not."
- The medical reasoning has to be the clinician's own. VHA policy requires a provider who
states causality to give a clear and specific rationale citing the evidence.
- An opinion with no rationale behind it is easy for an adjudicator to set aside. You paid for
paper, not for evidence.
What to bring instead: your dates of service, the in-service event or exposure in one paragraph,
the records that show it, when symptoms started, and the one sentence you need answered. Let the
clinician write the rest.
✅ Give them the facts. Let them reason.
Before you pay
The fee rules nobody shows you
Paid help is legal. Unaccredited help is not. Know the difference.
- Only VA-accredited attorneys, claims agents, and representatives of VA-recognized
organizations may represent you on a claim.
- A representative of a VA-recognized organization — a VSO — may not receive fees at
all.
- An accredited attorney or claims agent may charge only after the agency of original
jurisdiction issues notice of an initial decision, and only under a compliant written fee
agreement.
- On fee amount: up to 20 percent of past-due benefits is presumed reasonable; more
than 33 1/3 percent is presumed unreasonable. The rule is
38 CFR 14.636.
- Check accreditation before you pay anyone. VA's Office of General Counsel maintains
the accreditation search — look the person up by name.
Straight talk. I cannot point you to a VA rule saying a paid opinion gets discounted, and
I cannot point you to one saying it does not. So do not let anybody sell you either claim. What
VA's published rules actually turn on is the rationale and the factual accuracy of the opinion.
✅ Verify accreditation. Get it in writing.
You may not need one
Two situations where buying an opinion is wasted money
Veterans have paid for opinions on claims that never needed one.
- Presumptive conditions. Under
38 CFR 3.307 and 38 CFR 3.309, a presumptive disease is
considered incurred in service "even though there is no evidence of such disease during the
period of service." No nexus evidence from you at all.
- Claims that trip VA's duty to assist. Meet the low three-part threshold in route 1 and
VA must obtain the exam or opinion itself.
- Check the presumptive list for your service era, location and exposure before you
spend a dollar on an opinion.
Where a private opinion most often earns its keep: secondary service connection claims,
and after an unfavorable C&P exam. Those are the two fights where an outside
clinician's reasoning tends to change the picture.
✅ Check presumptives first. Free beats paid.
Secondary claims
The baseline step people forget
A secondary condition is one caused or worsened by a condition VA already pays you for.
- Under 38 CFR 3.310, a
secondary condition must be shown to be proximately due to or the result of a service-connected
disease or injury.
- For aggravation: an increase in a condition that is not service connected, proximately
due to a service-connected one, and not due to its natural progress.
- Aggravation also needs a medically established baseline — evidence of how severe the
condition was before the worsening began.
- An opinion that proves causation but never establishes the baseline can cost you the
aggravation award. Ask the clinician to address the baseline in writing.
✅ Causation plus baseline. Both.
Mental health claims
VA policy here points the other way
Read this before you ask your therapist for the form.
- For mental health DBQs, VHA Directive 1134(3) states it is recommended that the
veteran's treating provider not complete the DBQ, to maintain the integrity of the
patient-provider relationship.
- That is the opposite of the common advice that your own treating doctor is always the best
person to write it.
- What actually carries the opinion is an accurate and complete factual history and
sound reasoning — not the treating relationship itself.
- An outside clinician who reviews your full file can write an opinion every bit as strong.
If your treating provider declines a mental health DBQ, that is policy, not a judgment about your
claim. Ask VA to obtain the opinion under its duty to assist, or take the DBQ to another
qualified clinician.
✅ A no here is not a dead end.
No diagnosis yet
You do not need one in hand to file
Do not screen yourself out before you start.
- An opinion cannot substitute for a current disability. That part is true — there must be
something to rate.
- But VA's duty to assist is triggered by competent lay or medical evidence of a current
diagnosed disability or persistent or recurrent symptoms of a disability. Symptoms are
enough to start.
- A condition first diagnosed after discharge can still be service connected — see
38 CFR 3.303(d).
- File, describe the symptoms plainly, and let the exam establish the diagnosis.
✅ Symptoms are a starting point.
Deadlines
After a denial — the clock
A denial does not automatically mean you need a nexus letter. Sometimes it means the opposite.
- Higher-Level Review — a senior reviewer looks for an error of fact or law on the
existing record. VA's words: "You can't submit new evidence with a Higher-Level Review."
Deadline: within 1 year of VA's notice of the decision.
Details on VA.gov.
- Supplemental Claim — the path that takes new and relevant evidence, which is
where a medical opinion belongs. No deadline, but filing within 1 year protects your
original effective date, and effective date is money.
- Board Appeal — within 1 year of VA's notice of the decision.
Details on VA.gov.
- Contested claim — 60 days, and Board Appeal is the only option.
Read the denial before you spend money. If VA made an adjudication error on the record you
already gave them, a Higher-Level Review fixes it and needs no new opinion at all. If VA never
got a piece of evidence, a Supplemental Claim with that evidence is the move. Start at
va.gov/decision-reviews.
✅ Know which door before you pay.
My short version
In order, what I would do
- Check the presumptive lists for your era, location and exposure. If you are on one,
stop — you need no nexus evidence.
- File the claim and ask in writing that VA obtain the medical opinion under its duty
to assist. Name the condition and the in-service event.
- Sign VA Form 21-4142 and 21-4142a so VA can pull your private records for
free.
- Ask the provider you already see — VA or civilian — for a medical opinion using "at
least as likely as not." Bring the DBQ for your body system.
- Only after all of that, if the claim still needs an outside clinician, consider paying —
and verify accreditation and the fee agreement first.
- If you are denied, read why, then pick Higher-Level Review, Supplemental Claim or
Board Appeal on purpose, inside the deadline.
Never give up on a claim because one door closed. There is almost always another one. Free
routes come first, paid routes come last, and the deadline is the only thing you cannot get
back.
✅ Free first. Paid last. Never quit.