CO-31: Patient cannot be identified as our insured.
The payer's system cannot match the patient information submitted to any policy on file. This is often a data mismatch involving name, date of birth, or member ID rather than a true coverage gap.
What the group code means
- CO
- Contractual Obligation. The provider is responsible and the amount cannot be billed to the patient.
Why it fires
- The member ID, name, or date of birth submitted does not match the payer's enrollment file
- The patient has a new or different ID number than what was on file at registration
- A typo in the subscriber information occurred during claim entry
Corrective actions, ranked
- 1
Re-verify eligibility
Run a fresh eligibility check using the patient's current insurance card details.
- 2
Correct demographic data
Fix any typos in name, date of birth, or member ID and resubmit as a corrected claim.
- 3
Confirm the correct payer or plan
Make sure the claim was sent to the right plan within a large payer's system, such as the correct product line or state affiliate.
Is it worth appealing
Not an appeal. This is almost always a data-matching fix, so correct and resubmit rather than filing a formal appeal.
Other denial codes to check
Codes that share a remark code with this one, or that are reported under the same group code.
- CO-45Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.
- CO-97The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated.
- CO-16Claim/service lacks information or has submission/billing error(s).
- CO-11The diagnosis is inconsistent with the procedure.
- OA-18Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)
- CO-29The time limit for filing has expired.
Retrieved 2026-07-18.
Do not let this happen again
Scrub the claim against NCCI PTP and MUE edits before you submit, free and in your browser.
Denial7 provides billing and administrative guidance based on published CMS and X12 sources. It is not medical advice, not a coverage determination, and not a guarantee of payment. NCCI and MUE edits are republished quarterly and payer policies vary by contract. Always confirm against the payer's own current policy before submitting or appealing.