Glossary · Denial and adjustment codes
What is denial code CO-109?
CO-109 means the claim went to a payer that doesn't cover the service and must be sent to the correct payer or contractor, such as a different Medicare jurisdiction or a managed care plan.
Example · fictional data
A Medicare claim sent to original Medicare for a patient enrolled in a Medicare Advantage plan.
Remittance advice, claim line
- Billed to
- Medicare Part B
- Patient enrolled in
- Example Medicare Advantage HMO since 01/01/2026
| Service | Billed | Paid | Adjustment |
|---|---|---|---|
| 99214 Office visit | $210.00 | $0.00 | CO-109 $210.00 |
- Medicare Advantage plans pay instead of original Medicare. Bill the plan, attaching this denial if its filing limit is close.
Reason code 109 reads: Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor.
Common causes
- The patient moved to a Medicare Advantage or managed Medicaid plan, and the claim went to original Medicare or fee-for-service Medicaid.
- The service belongs to a different Medicare contractor, such as a DME MAC instead of the Part B MAC.
- The plan carves certain services out to a separate vendor, such as behavioral health or lab.
- A typo in the payer ID sent the claim to the wrong place.
How to resolve it
Identify the correct payer through an eligibility check, bill it, and keep the denial: many payers accept proof of the first submission when the claim arrives close to its timely filing limit.
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