CO 224 denial code

Claim adjustment reason code 224. Often reported as CO 224.

Member identity must be confirmed

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 224 means

The payer has flagged the member's identity as stolen or misused and will hold claims until the patient proves who they are.

The payer has a record that the member's identity was stolen or misused. It will not process claims until the patient's identity is confirmed.

Expect this flag to affect later claims for the same member too, so fix the verification once rather than claim by claim.

Group codes seen with 224

On a remittance, 224 comes after a group code. These are the ones it is most often reported with:

• CO 224 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The member reported identity theft and the payer added a flag.
• The payer detected unusual activity on the member's ID.
• Demographics on the claim did not match the payer's verified record.

What to do next

1. Confirm the patient's identity at the next visit with photo ID and insurance card.
2. Contact the payer to learn what verification it accepts and how to send it.
3. Resubmit the claim once the payer confirms the verification is on file.
4. Alert your compliance team if you suspect someone used the patient's identity at your practice.

Related codes

• 16 (reason code) Missing information or billing error
• 31 (reason code) Payer cannot identify the patient