CO-31 — Patient Not Eligible / Cannot Be Identified as Insured
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 per…
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In plain language
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.
Start here
Review the RARC for the specific missing/incorrect identifier.
Who resolves it
Registration/Patient Access or Billing
Who prevents it
Registration/Patient Access — real-time eligibility verification at scheduling and check-in.
Sources
- X12 CARC list; X12 RARC list
Validated ClaimetryX Source — Denial Management Knowledge Base, 2026 Research Edition
Research date August 18, 2026. CARC/RARC combinations and payer processes vary. Always check the specific remittance advice and the payer's current requirements before acting on any denial.
Published by ClaimetryX. Sources identify the code standards, agency guidance, and payer policies supporting this reference. How we use sources
How to resolve this denial, step by step
- 1
Review the RARC for the specific missing/incorrect identifier.
- 2
Run a fresh real-time eligibility check for the date of service.
- 3
Compare the eligibility response to what was submitted on the claim.
- 4
If a data-entry error is found, correct and resubmit the corrected claim.
- 5
If the patient was not covered on that plan, determine correct payer/self-pay status and rebill or bill patient per registration findings.
- 6
Document the eligibility verification outcome.
- 7
Escalate to Patient Access if the same registration error recurs for the same front-desk workflow.
Then choose the correct disposition
Eligibility correction / corrected claim
when the ID or plan data was wrong.
COB correction
if patient is actually covered by a different payer (cross-reference D25).
Patient responsibility
only after confirming the patient truly had no active coverage for the date of service.
Stop and escalate when
- Eligibility response conflicts with payer portal data (system discrepancy); patient disputes coverage status; retroactive eligibility/Medicaid determination pending.
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.
Do Not Do This
- Do not bill the patient before confirming actual coverage status through eligibility verification.
- Do not alter the date of service to fit an eligibility window.
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.
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.
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.
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.
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.
AI Answer Guardrail
- Confirm current, date-of-service-specific eligibility through a real-time payer response before recommending a corrected claim or patient billing.
AI Search Terms / Synonyms
- CO31; CO-31; patient not eligible; cannot identify insured; eligibility denial; member ID mismatch.
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