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.
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
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.
Found this code on your bill or EOB?
Upload the document — MD Bill Check decodes every code, checks the math line by line, and explains what's worth questioning.