CO-31CO group · Eligibility

CO-31 denial code: patient cannot be identified as our insured

CO-31 means the claim reached a payer that has never heard of this patient — which is as often about which payer as about which patient.

CO-31 fires when the demographics submitted do not resolve to a member record at that payer. It is an identity edit, and the two live possibilities are a data mismatch or a claim sent to the wrong entity entirely.

What CO-31 means

Payers match on a combination of member identifier, name and date of birth, and a mismatch in any of them can fail the lookup. But the cause practices under-diagnose is routing: large carriers operate many legal entities and plan lines, and a card that carries a familiar brand may point at an entity that is not the one your clearinghouse addressed. The payer identifier on the card, not the logo, is what determines where the claim should go.

Why CO-31 fires

  • The member identifier was transcribed with or without a prefix the payer requires.
  • Name or date of birth do not match the enrolment record.
  • The claim was routed to the wrong entity or plan line of a multi-entity carrier.
  • Coverage had not yet been loaded when the claim was submitted.

Is CO-31 worth appealing?

Sometimes worth appealing

Re-verify eligibility and routing before resubmitting. Where eligibility can be evidenced for the date of service, send that evidence with the resubmission rather than the same claim again.

How to resolve or appeal CO-31

  1. 1

    Run a fresh eligibility check

    For the date of service, not today, and capture the response as evidence.

  2. 2

    Confirm the payer identifier

    Check the identifier on the card against the one the claim was routed to; brand names are not routing.

CO-31 — frequently asked

Why does the patient say they were covered?
They often were — with a different entity of the same carrier, or with coverage loaded after the visit. Both produce this edit and neither is the patient being wrong.
Is this appealable?
There is nothing to appeal until the claim reaches a record. Establish eligibility and routing first; only a payer that denies coverage it can be shown to have provided is an appeal.

Related guides

CO-140 · AdministrativePR-31 · EligibilityCO-27 · Eligibility

Sources

Reason-code meanings are paraphrased from the X12 Claim Adjustment Reason Code list for plain-language reference; they are not reproduced verbatim. This is general information, not legal, coding, or medical advice — always confirm against the payer's remittance and policy.

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