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CO-109 Denial Code: Claim Sent to the Wrong Payer

CO-109 means the claim or service is not covered by the payer or contractor you sent it to, and you must send it to the correct payer or contractor. It is a routing problem: another plan, MAC, or program is responsible for this service or patient.

Quick facts

Code
CO-109 (CARC 109)
Status
Active In use since January 1, 1995; last modified January 29, 2012.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The payer that received the claim is not responsible. You should not bill the patient; bill the correct payer instead.
  • OA (Other Adjustment): Sometimes used because the adjustment is administrative rather than a liability decision. The next step is the same: refile to the correct payer.
Official description
Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-109 means

CARC 109 says the claim/service is not covered by this payer/contractor, and you must send it to the correct payer/contractor. Unlike a coverage denial, it does not judge the service. It says you sent the claim to the wrong place.

“Wrong place” can mean a completely different insurer, but it often means a different part of the same system: another Medicare Administrative Contractor (MAC), the DME MAC instead of the Part B MAC, a Medicaid managed care plan instead of fee-for-service Medicaid, or a delegated vendor that handles a carved-out benefit.

Example: a practice bills Original Medicare for a patient who enrolled in a Medicare Advantage plan the previous month. The MAC returns CO-109. The practice checks eligibility, finds the MA plan, and files there.

Common causes

  • The patient changed coverage, for example joined a Medicare Advantage plan or Medicaid managed care plan, and the claim went to the old payer.
  • The claim went to the wrong Medicare contractor because of the service location or the type of service (Part A vs. Part B, DME MAC vs. A/B MAC).
  • A carved-out benefit (behavioral health, vision, lab, radiology, pharmacy) is administered by a different company than the medical plan.
  • The member ID card shows one payer, but claims are routed to a separate administrator or network.
  • A special program is responsible, such as the Black Lung Program, VA community care, or a workers’ compensation carrier.
  • Clearinghouse payer ID mapping sent the claim to a similarly named plan.

How to fix it

  1. Run eligibility for the date of service to identify the responsible payer. Check for Medicare Advantage, Medicaid managed care, and carve-out administrators.
  2. Read the remark code. N104, M11, MA16, and similar remarks often name the correct contractor or program.
  3. File a new, original claim to the correct payer. It is not a corrected claim for the original payer, so do not use resubmission code 7 there.
  4. Mind the filing deadline of the correct payer. Attach or keep the CO-109 remittance as proof of timely filing elsewhere if the payer accepts it. See our timely filing guide.
  5. Appeal the CO-109 only if the original payer was in fact responsible on the date of service, with the eligibility proof.
  6. Update the patient’s insurance record so future claims route correctly.

How to prevent it

  • Verify eligibility before every visit, not just at intake. Coverage changes, especially at the start of a month or plan year.
  • Ask patients directly whether they joined a new plan, including Medicare Advantage or Medicaid managed care.
  • Keep a list of carve-out administrators for each major plan in your market.
  • Audit payer ID mappings in your clearinghouse after any plan mergers or renames.
  • Our guide to eligibility and COB denials walks through a verification routine that prevents most wrong-payer claims.

Specialty notes

Behavioral health is often carved out of the medical plan to a separate managed behavioral health organization, so a medical plan CO-109 on a therapy claim usually means the carve-out handles it. DME suppliers billing Medicare must use the DME MAC for the patient’s permanent address, not the practice location.

Remark codes that may appear with CO-109

  • N104 (This claim/service is not payable under our claims jurisdiction area.): Medicare jurisdiction issue: the claim belongs with a different Medicare contractor.
  • N747 (This is a misdirected claim/service.): Misdirected claim: submit it to the plan where the patient resides.
  • M11 (DME, orthotics and prosthetics must be billed to the DME carrier who services the patient's zip code.): DMEPOS items must go to the DME contractor serving the patient's area.
  • MA16 (The patient is covered by the Black Lung Program.): The patient is covered by the Black Lung Program, so the Department of Labor is the correct payer.
  • N52 (Patient not enrolled in the billing provider's managed care plan on the date of service.): The patient is not enrolled in the billing provider's managed care plan on the date of service.
  • OA-22 (This care may be covered by another payer per coordination of benefits.): Another payer may be primary under coordination of benefits, a primacy question rather than a routing one.
  • CO-31 (Patient cannot be identified as our insured.): The patient cannot be identified as the payer's insured.
  • CO-B11 (The claim/service has been transferred to the proper payer/processor for processing.): The payer transferred the claim to the proper payer itself, instead of sending it back.
  • OA-19 (This is a work-related injury/illness and thus the liability of the Worker's Compensation Carrier.): Work-related injury that belongs with the workers' compensation carrier.
  • OA-24 (Charges are covered under a capitation agreement/managed care plan.): Covered under a capitation or managed care arrangement.

CO-109 FAQ

Does CO-109 stop the timely filing clock?

Not automatically. Timely filing limits are set by the correct payer, and many do not extend them because the claim went elsewhere first. Keep the CO-109 remittance as proof of your original filing date in case the correct payer accepts it.

Should I appeal a CO-109?

Only if you are sure this payer is responsible, for example eligibility shows active coverage with them on the date of service. Otherwise the fix is to file with the correct payer.

Why do Medicare Advantage patients cause CO-109?

When a Medicare beneficiary is enrolled in a Medicare Advantage plan, the plan generally pays for covered services instead of Original Medicare, so claims sent to the MAC may be returned for the correct payer.

Can I bill the patient for CO-109?

No. The service may well be covered, just by a different payer. Find that payer first.