Reviewed by Jonathan Teplitsky · Updated August 2026
Nexus Letter vs. DBQ: The Short Answer
A nexus letter and a DBQ answer two different questions in your VA claim. A nexus letter proves your condition is connected to your service. A DBQ documents how severe that condition is today.
Veterans often think these two documents do the same job. They don't. Confusing them can leave a real gap in your evidence.
This guide breaks down what each document does and who writes it. We also cover the cost, the evidence weight, and why many claims need both.
What Is a Nexus Letter?
A nexus letter is a written medical opinion. It links your current condition to an event, injury, or exposure during your military service. A doctor writes it after reviewing your medical and service records.
The letter must state a clear opinion on causation. VA raters look for language like "at least as likely as not" connected to service. A vague opinion without reasoning carries little weight.
A nexus letter is not a standardized VA form. Its length and structure can vary by doctor. It must still cover the diagnosis, the opinion, and the medical reasoning behind it.
See our nexus letter guide for what a strong letter must include. Our nexus letter template gives your doctor a starting structure.
What Is a DBQ?
A DBQ (Disability Benefits Questionnaire) is a standardized VA form. It documents a condition's current symptoms, severity, and functional impact. Each condition, from knees to PTSD, has its own DBQ template.
The VA publishes official DBQ templates on VA.gov, organized by condition. A licensed provider fills in the form with checked boxes and test results. It does not include a written opinion on cause.
A DBQ can be completed at a VA-scheduled C&P exam. Your own private provider can also complete it, using the same official template. Either way, the form itself never sets a disability rating.
Nexus Letter vs. DBQ: Comparison Table
The table below lines up both documents side by side. Use it to see exactly where they overlap and where they differ.
| Factor | Nexus Letter | DBQ |
|---|---|---|
| What it proves | Cause: links your condition to military service | Severity: documents current symptoms and functional limits |
| Who writes it | Your own private doctor or specialist | A VA C&P examiner, contractor, or your own private provider |
| Format | A written medical opinion letter, not a fixed template | A standardized VA form specific to your condition |
| Required or optional | Optional, but often necessary to prove service connection | Not required to file; the VA gets one anyway through a C&P exam |
| Typical cost | Usually paid out of pocket for a private specialist | Free at a VA C&P exam; a private DBQ can cost money |
| Sets your rating percentage? | No; it addresses service connection only | No; a rater applies 38 CFR Part 4 to the findings |
Who Writes Each Document
A nexus letter almost always comes from a private doctor you choose and pay. VA C&P examiners rarely write standalone nexus letters for veterans to keep. Their exam report may still include a service-connection opinion if the VA specifically requested one.
A DBQ has two possible authors. The VA schedules a C&P exam, where its own examiner or contractor completes the form for free. Your own treating provider can also complete the same official form.
When You Need a Nexus Letter
You need a nexus letter when your condition's cause is not obvious from the record alone. This is common for conditions that developed slowly over time. It's also common for secondary conditions caused by an already-rated disability.
A nexus letter matters most after a denial for lack of a medical opinion on service connection. It also helps when service records don't clearly document the original injury or exposure.
When You Need a DBQ
You need a DBQ when the VA requires current evidence of how severe your condition is. This applies to every claim, first-time or an increase request.
The VA schedules a C&P exam and completes a DBQ for you in most cases. Submitting your own private DBQ can speed up the process. It can also add detail a rushed exam might miss.
Do You Need Both?
Most first-time claims need both a nexus letter and a DBQ. One proves the condition came from your service. The other proves how severe it is today.
Think of these as two separate arguments a VA rater must accept. Service connection answers whether the military caused the condition. A rating percentage answers how much it limits you now.
A DBQ alone can't answer the service-connection question. A nexus letter alone can't set your severity rating. Most veterans need both documents working together.
There are exceptions. If your condition is on the VA's presumptive list, service connection may already be assumed. In that case, a DBQ or C&P exam alone may be enough to establish severity.
Sometimes only the cause is disputed. If your diagnosis and severity are already clear, a nexus letter alone may close the gap. A missing nexus letter is a common reason claims get denied for lack of service connection.
Example: Sleep Apnea Secondary to PTSD
Here's how the two documents work together in a real scenario. A veteran has a service-connected PTSD rating and later develops sleep apnea. The VA needs proof the sleep apnea links to the PTSD, not just proof it exists.
A sleep study documents the diagnosis and severity. That's DBQ territory. The sleep study alone doesn't explain why the sleep apnea developed.
A nexus letter fills that gap by explaining the medical link between PTSD and sleep apnea. Without that letter, the claim often gets denied, even with a well-documented, severe case of sleep apnea.
How to Get Each Document
Getting a DBQ starts with either your C&P exam or your own doctor. If you wait, the VA schedules the exam and completes the matching DBQ for free.
If you go the private route, download the correct condition-specific DBQ from VA.gov and bring it to your appointment. Ask your provider to review your records first; a thorough DBQ carries more weight than a rushed one.
Getting a nexus letter takes more legwork. Look for a doctor familiar with your condition, often a specialist rather than a general practitioner. Some specialists advertise nexus letter services specifically for veterans, though you can also ask your own treating doctor first.
Give that doctor your full service treatment records, not just your current medical file. A nexus letter written without service records rarely has the detail a rater needs to find it persuasive.
Evidentiary Weight: Which One Carries More?
Neither document outweighs the other, because they answer different questions. A rater cannot use a DBQ to establish cause. A rater cannot use a nexus letter to set a severity percentage.
A nexus letter carries weight based on its medical reasoning. A vague opinion carries little weight, even from a qualified doctor. A DBQ carries weight based on how thorough and current its findings are.
A private DBQ or nexus letter isn't automatically weaker than one from a C&P exam. Raters weigh the quality of the medical reasoning and the thoroughness of the exam, not simply who scheduled it.
What to Do Next
Your next step depends on which question your claim still needs answered. If service connection is the weak point, work with your doctor using our nexus letter template.
If severity is the weak point, review our C&P exam tips before your appointment. Many veterans strengthen a claim by preparing both documents at the same time.
Don't wait for a denial letter to find out which piece was missing. Ask your accredited representative which element is weak before the VA rules on your case.
Sources
VA.gov: Evidence needed for your claim. VA.gov: VA claim exam (C&P exam). 38 CFR Part 4 (Schedule for Rating Disabilities).
Frequently asked questions about nexus letters and DBQs
Can a private doctor complete a DBQ? Yes. Any licensed provider can complete the official VA DBQ form for your condition. It doesn't have to be a VA examiner.
Does a nexus letter replace the C&P exam? Not usually. The VA can still schedule a C&P exam after you submit a nexus letter. This often happens when current severity also needs documenting.
Which one determines my rating percentage? Neither one directly sets it. A VA rater applies 38 CFR Part 4 to the DBQ or exam findings. The nexus letter only affects whether the claim gets service-connected at all.
Do I have to pay for a nexus letter? Usually, yes, if you use a private specialist. Costs vary by provider and by how complex your condition is. The VA does not reimburse this expense.
Is a DBQ required to file a claim? No. You can file without submitting one yourself. The VA will schedule a C&P exam to gather the same information.
What happens if I only submit a nexus letter? The VA may still schedule a C&P exam. It needs current evidence of your condition's severity. A nexus letter alone doesn't set a rating percentage.