Denial Code Decoder
CO-109 — Wrong payer for this service
The payer says this claim belongs to a different payer or contractor — the service is not covered by THIS plan, though it may be covered elsewhere: a different line of business, a carve-out vendor, or a different Medicare contractor.
Billable to the patient? Not on this denial — the claim has not been adjudicated by the responsible payer yet.
Where this denial is born
- Front desk
- Coding
- Claim build
- Submission
- Adjudication
This denial is usually created at the highlighted stage — that is where prevention lives.
Answer the questions — follow the path
The same questions an experienced biller asks, in order. Your answers draw the route to the right action.
Can you identify the responsible payer?
The eligibility response, the member card, or payer support will name the carve-out or correct contractor.
The full decision tree
Can you identify the responsible payer?
The eligibility response, the member card, or payer support will name the carve-out or correct contractor.
- Yes →
Bill the responsible payer. Submit to the correct payer or contractor — mind ITS timely filing limit, which has been running since the date of service.
- No →
Trace the coverage. Call the denying payer and ask where the service is covered; verify with the patient's employer plan documents if needed.
Prevention
Read the eligibility response's plan and carve-out details, not just the active/inactive flag — behavioral health, labs, and DME are routinely carved out to other payers.
Related reading
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