CO 189 denial code

Claim adjustment reason code 189. Often reported as CO 189.

Unlisted code used, specific code exists

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 189 means

The payer will not pay because an unlisted or not otherwise classified code was billed when a specific code exists.

Unlisted and not otherwise classified codes are meant for services with no specific code. This code means the payer believes a specific code covers what you billed.

Review the record and the code set for a code that describes the service, and send a corrected claim with it.

Group codes seen with 189

On a remittance, 189 comes after a group code. These are the ones it is most often reported with:

• CO 189 (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

• An unlisted code was used out of habit when a specific code was available.
• A new specific code took effect and billing still used the unlisted code.
• The service description led the payer to a specific code.

What to do next

1. Search the code set for a specific code that matches the documented service.
2. Resubmit a corrected claim with the specific code.
3. Appeal with the record and a clear explanation if no specific code fits.

Related codes

• 181 (reason code) Procedure code invalid on date of service
• 16 (reason code) Missing information or billing error