Denial Code 31 (CO-31, PR-31) — Meaning & What to Do
Claim Adjustment Reason Code (CARC)
What denial code 31 means: The patient couldn't be identified as covered by this insurer.
What to do about denial code 31: Verify your member ID and that the correct insurance was billed.
CO-31 vs PR-31 vs OA-31: what the prefix means
| Code on your EOB | What the prefix means | Who typically pays |
|---|---|---|
| CO-31 | Contractual obligation — the provider writes the amount off | Usually not the patient |
| PR-31 | Patient responsibility | The patient |
| OA-31 | Other adjustment | Often another payer or plan |
The prefix tells you who is expected to absorb the amount; the number (31) tells you why.
Seeing denial code 31 on your EOB?
A denial code tells you what the payer reported, but it may not tell the whole story. Reviewing your EOB and bill together can help clarify what may need attention.
Related codes
CARC 26Expenses were incurred before your coverage started.
CARC 35You've reached the lifetime benefit maximum for this service.
CARC 24Charges are covered under a capitation or managed-care arrangement.
CARC 39Authorization was requested but denied for this service.
Keep reviewing your bill
- Medical Bill vs EOB: What Is the Difference?
- How to Dispute a Medical Bill — Find Billing Errors Before You Pay
- What Is an Itemized Medical Bill? How to Request One
Frequently asked questions about Denial code 31
What does denial code 31 mean on my EOB?
The patient couldn't be identified as covered by this insurer.
What should I do about denial code 31?
Verify your member ID and that the correct insurance was billed.
Seeing this code on your own EOB?
Upload the EOB, the bill, or both — MD Bill Check reads the codes on your documents, compares them side by side, and flags what's worth questioning. Free, no account needed.