CO 31 Denial Code: Patient Not Identified

Official CARC description: “Patient cannot be identified as our insured.” Here’s what it actually means, why it fires, and how to get the claim paid.

Contractual Obligation (CO)Fix steps belowFree appeal letter draftNo PHI needed

What CO 31 actually means

The payer can't match the person on the claim to a member. Almost always a data hygiene issue — ID typos, name changes, or the wrong plan's card scanned at intake.

Liability group: CO = Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.

Why CO 31 fires

How to fix CO 31

1

Step 1

Re-scan the card; verify ID, name spelling, DOB against the 271 response

2

Step 2

Correct and resubmit — this is not an appeal

3

Step 3

No match anywhere: run a coverage-discovery check, then patient outreach

4

Step 4

Tighten front-desk card capture (photo both sides, verify at every visit)

Appeal it — or fix and resubmit?

No appeal path — only correction. Protect timely filing by documenting the original submission while you chase the right identity/payer.

Draft a CO 31 appeal letter now ↓

Draft the appeal letter

Fill in the denial facts — use placeholders, never real patient data (the letter keeps [PATIENT NAME]-style fields so you can merge real details privately). A payer-ready draft with an enclosure checklist comes back in ~20 seconds.

Your appeal letter draft will appear here.

Frequently asked questions

What does denial code CO 31 mean?

Patient cannot be identified as our insured. In practice: The payer can't match the person on the claim to a member. Almost always a data hygiene issue — ID typos, name changes, or the wrong plan's card scanned at intake.

Is CO 31 the provider’s write-off or the patient’s responsibility?

CO stands for Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.

Can you appeal a CO 31 denial?

No appeal path — only correction. Protect timely filing by documenting the original submission while you chase the right identity/payer.

Related denial codes