CO 109 denial code

Claim adjustment reason code 109. Often reported as CO 109.

Not covered by this payer, send elsewhere

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 109 means

This payer is not responsible for the claim or service and expects you to send it to the payer or contractor that is.

The payer is not saying the service is uncovered in general. It is saying it is the wrong place to send it. Another plan, a different contractor or region, a managed care plan, or a separate benefit manager is responsible for this patient or service.

Check the remark codes, which often name the type of entity to bill. Common examples are a patient enrolled in a managed care plan, a service handled by a carve-out vendor, or a claim sent to the wrong regional processor. Billing the patient is usually not the next step; finding the right payer is.

Group codes seen with 109

On a remittance, 109 comes after a group code. These are the ones it is most often reported with:

• CO 109 (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 patient is enrolled in a managed care or replacement plan that pays these services instead.
• The service is carved out to a separate vendor, such as a behavioral health, pharmacy or vision manager.
• The claim went to the wrong regional contractor or processing jurisdiction for the provider or service.
• The patient's coverage with this payer ended or the member was on another plan on the date of service.
• A different payer is primary or responsible, such as workers' compensation or liability coverage.

What to do next

1. Run an eligibility check for the date of service to find the plan or contractor that is responsible.
2. Read the remark codes on the line for clues about which entity to bill.
3. Submit the claim to the correct payer or contractor and keep the denial as proof of timely filing.
4. Update the patient's insurance in your system so future claims go to the right place.
5. Ask the patient about other coverage if eligibility tools do not show the responsible plan.

Related codes

• 22 (reason code) Another payer may be primary
• 24 (reason code) Covered under capitation or managed care
• 27 (reason code) Service after coverage ended
• 96 (reason code) Service not covered by the plan