CO-31 / PR-31 Denial Code: Patient Cannot Be Identified As Our Insured
CARC 31 means the patient cannot be identified as the payer's insured — the demographic or member ID data submitted did not match an active enrollee. It usually posts as PR-31 (patient responsibility) because no coverage was verified, though it is best treated as a correctable eligibility error rather than a true bill-the-patient event.
- Group
- PR — Patient Responsibility (sometimes CO)
- Category
- Eligibility / patient identification
- Appealable?
- No — correct the demographics and resubmit
- Typical fix
- Re-verify eligibility, fix member ID/DOB/name, resubmit
What does denial code CARC 31 mean?
CARC 31 is the payer saying: the person on this claim does not match anyone we insure. The official X12 description is "Patient cannot be identified as our insured." It fires when the member ID, name, date of birth, or plan submitted does not line up with an active enrollee record. It most often carries the PR group code, but the amount is not a real patient balance until you prove coverage was actually absent.
Because the claim never reached benefit adjudication, CARC 31 is an eligibility problem, not a payment decision. Treat it like CO-16 family of front-end rejections rather than a denial you argue on merits.
Why does CARC 31 happen?
- Member ID errors — a transposed digit or a dropped alpha prefix on the subscriber ID.
- Name or DOB mismatch — the patient's legal name or birth date differs from the payer's enrollment file.
- Wrong payer or plan — the claim went to the prior carrier, or to the wrong plan after a coordination of benefits change.
- Coverage lapsed — the patient genuinely was not enrolled on the date of service.
Mini-example: 99213 ($92) submitted under member ID W1234567 for "Jon Smith." The ERA returns the line with PR-31 and no payment because the enrollment record reads "John Smith, ID W7234567." The $92 is not a patient balance — it is a keying error.
How do you work a CARC 31?
- Run a fresh real-time eligibility check for the date of service and capture the exact member ID, name, and DOB on file.
- Compare every demographic field on the claim against that response and correct any mismatch.
- Confirm the claim went to the correct payer and plan — check for a newer card or a COB change.
- Resubmit as a corrected claim; if coverage truly did not exist, rebill the correct payer or bill the patient.
How do you prevent CARC 31?
Verify eligibility at every visit, not just at intake, and scan the insurance card front and back to capture the exact ID and prefix. Re-run eligibility when a patient mentions a job change, marriage, or new plan. Route unfamiliar codes through the denial code lookup so eligibility rejections are not mistaken for benefit denials, and reconcile timely filing clocks since correction cycles eat into the window.
Frequently asked questions
Not immediately. Although CARC 31 carries the PR group code, it almost always signals a data-entry or eligibility error rather than a genuine non-covered service. Re-verify the member ID, name, and date of birth against the payer's system first. Only pursue the patient after confirming they truly had no coverage on the date of service.
No. There is nothing to appeal because the payer never identified the member. The remedy is a corrected claim with accurate demographics — right member ID, spelling, date of birth, and payer. If you resubmit with the same wrong data it will deny again, so verify eligibility before you refile.
Common causes are a transposed member ID, a name that does not match the subscriber record, wrong date of birth, or the claim routed to the wrong payer or plan. Coordination-of-benefits changes and mid-year plan switches also trigger it. Pull a fresh eligibility response and reconcile every field before refiling.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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