CO-31 — Patient Not Eligible / Cannot Be Identified as Insured

Denial Identifier

• Primary CARC: CO-31 — "Patient cannot be identified as our insured." (X12)
• Related eligibility CARCs: 177 (patient has not met required eligibility requirements), 178 (spend-down requirements), 179 (waiting period requirements), 180 (residency requirements), 32 (patient not an eligible dependent), 33 (insured has no dependent coverage)
• Common RARCs: N30 (patient ineligible for this service), MA27 (missing/incomplete/invalid entitlement number or name), N517 (resubmit a new claim with the requested information)
• Group code for CARC 31 is payer-determined (may appear as CO or PR); verify on the specific remittance.

Plain-Language Meaning

• The payer cannot match the patient/member information on the claim to an active member on their system — either the ID is wrong, the patient is not covered by that plan, or an eligibility condition (waiting period, residency, spend-down) was not met.

Why the Claim Was Denied

• Registration: wrong Member ID, subscriber name mismatch, wrong payer selected at check-in
• Eligibility: patient not actually enrolled in the billed plan on the date of service; plan- specific waiting period not yet satisfied
• Payer processing: payer system lag in loading newly effective enrollment

Information the Biller Must Review

• Patient name, DOB, Member ID, group number, insurance card image, real-time eligibility (270/271) response, payer portal eligibility screen, coverage effective dates.

What Needs to Be Corrected

• Claim correction: Correct Member ID/name/group number and resubmit as a corrected claim if the plan is in fact active and the data was simply mis-keyed.
• Upstream correction: If the patient genuinely is not eligible under that plan/ID, registration must re-verify insurance at the point of service; this is not a claim-data fix.

Resolution Workflow

• Review the RARC for the specific missing/incorrect identifier.
• Run a fresh real-time eligibility check for the date of service.
• Compare the eligibility response to what was submitted on the claim.
• If a data-entry error is found, correct and resubmit the corrected claim.
• If the patient was not covered on that plan, determine correct payer/self-pay status and rebill or bill patient per registration findings.
• Document the eligibility verification outcome.
• Escalate to Patient Access if the same registration error recurs for the same front-desk workflow.

Department Most Likely Responsible

• Resolves current claim: Registration/Patient Access or Billing. Prevents recurrence:
• Registration/Patient Access — real-time eligibility verification at scheduling and check-in.

Prevention Control

• Real-time (270/271) eligibility verification before the visit; insurance card image capture and comparison; scheduling-system alerts for expired or unverified coverage.

Escalation Trigger

• Eligibility response conflicts with payer portal data (system discrepancy); patient disputes coverage status; retroactive eligibility/Medicaid determination pending.

Sample Scenario

• Scenario: Claim denied CO-31.
• Finding: Member ID was transposed by one digit during check-in; real-time eligibility confirms active coverage under the correct ID.
• Action: Corrected claim submitted with accurate Member ID.

Resolution path at a glance

AI Search Terms / Synonyms

• CO31; CO-31; patient not eligible; cannot identify insured; eligibility denial; member ID mismatch.

AI Answer Guardrail

• Confirm current, date-of-service-specific eligibility through a real-time payer response before recommending a corrected claim or patient billing.

Sources

• X12 CARC list; X12 RARC list