Denial code

CO-109 denial code: send the claim to the correct payer

CO-109 is a claim adjustment reason code that says the claim or service is not covered by this payer or contractor and you must send it to the correct one. No appeal to the same payer will change who pays, so the work is finding the right payer fast.

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Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · Last reviewed October 2026

CO-109 at a glance

Code typeCARC, group code CO or PR as shown on the remit

DescriptorClaim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor.

X12 start date01/01/1995 (last modified 01/29/2012)

RARCs that explain itN104, N418, N105

Claim fieldCMS-1500 item 32 service location

Filing clockWrongly sent submission is not a Medicare claim until the right contractor receives it

Fix pathEligibility check, then a new claim to the right payer

In short: CO-109 means you sent the claim to a payer or contractor that does not process it. Identify the right one through an eligibility check, then submit a new claim there. Medicare does not treat a wrongly sent submission as a claim until the correct contractor receives it, so the filing clock keeps running.

What does CO-109 mean?

X12 defines claim adjustment reason code (CARC) 109 as: "Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor." The start date is 01/01/1995 and it was last modified on 01/29/2012.

It is a routing denial. It differs from CO-22, where another payer may be responsible by coordination of benefits, and from CARC 24, "Charges are covered under a capitation agreement/managed care plan."

Which remark codes explain a CO-109?

RARC	X12 wording	What it points to
N104	This claim/service is not payable under our claims jurisdiction area. You can identify the correct Medicare contractor through the CMS website at www.cms.gov.	A Medicare jurisdiction mismatch.
N418	Misrouted claim. See the payer's claim submission instructions.	A payer routing rule in its manual.
N105	This is a misdirected claim/service for an RRB beneficiary. Submit paper claims to the RRB carrier and call the number given.	A Railroad Retirement Board beneficiary.

How does Medicare decide which contractor gets the claim?

Medicare Claims Processing Manual chapter 1, section 10, says in general institutional providers go to the Part A side and physicians, individual practitioners, ambulance suppliers, ASCs, DME suppliers and IDTFs go to the Part B side. Section 10.1.1 says that for services paid under the physician fee schedule and for anesthesia, jurisdiction follows the payment locality where the service was furnished, based on the ZIP code.

When a practitioner furnishes services in localities that span more than one A/B MAC, the chapter requires separate claims to the appropriate MAC. Chapter 26 says item 32 of the CMS-1500 holds the service location. Section 70.2.1 says it is the provider's responsibility to submit each claim to the appropriate contractor.

Medicare Advantage is a separate route. The MLN fact sheet MLN8816413 says the eligibility response for an MA enrollee shows the plan, with enrollment effective and termination dates, and says to direct your query to that plan. Chapter 1, section 90, says status at admission decides liability for an inpatient acute care stay. See Medicare Advantage.

How do you find the right payer after CO-109?

Run eligibility for the service date

Use the Medicare MAC portal, HETS or your clearinghouse. The response names the MA plan or the Medicare entitlement, and the MSP record if another payer is primary.

Read the payer's routing rule

For N418, open the payer's claim submission instructions. For N104, find the Medicare contractor through the CMS site.

Send a new claim to the right payer

Do not appeal. An appeal to the denying payer does not change who is responsible.

Watch the filing limit

Chapter 1, section 70.2.1, says re-routed services are not claims until the right contractor receives them. Check CO-29 and the exceptions there before the limit passes.

How does CO-109 read on the remittance?

CO-109 says the payer you billed is the wrong one for this claim. The remark (N104, N418 or N105 on the page above) tells you more, and it sits in the LQ segment of the line or in MOA or MIA for the whole claim. The group code is CO, so the adjustment is contractual and the patient is not billed. The page above lists the Medicare claim rules for a claim sent to the wrong place; check the plan on the claim against eligibility first.

A simplified remittance line with the group code, claim adjustment reason code, adjustment amount and remark code marked — Simplified, not a real 835. CO-109 is a routing problem.

Example: made-up amounts, illustrative only

A claim for a patient with a different plan returns CO-109 for $240.00.

CheckEligibility on the date of service

ActSend the claim to the plan named by the eligibility response. Do not appeal.

Where does CO-109 show up most?

It is common in ambulatory surgery center billing, where Part B jurisdiction applies, in hospitalist billing and in home health billing. Its neighbours are CO-151, CO-97 and CO-167. If these denials keep coming back, our denial management team can work them.

CO-22 Another payer may be responsible CO-97 Included in another service's payment CO-167 Diagnosis not covered

Sources

We check every rule, code and deadline against the official source. See our editorial policy.

FAQ

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Straight answers from the team that does the work.

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01How do I find the right payer after CO-109?

Run an eligibility check for the service date through the MAC portal, HETS or your clearinghouse. For a Medicare Advantage enrollee the response names the plan and its enrollment dates, and you direct the claim to that plan. For N418, read the payer's claim submission instructions.

02Should I appeal a CO-109?

No. CO-109 says the claim must be sent to the correct payer, so an appeal to the same payer does not change who is responsible. Identify the right payer and submit a new claim there, and keep the filing limit in view.

03What does N104 mean with a CO-109?

X12 words N104 as this claim or service is not payable under our claims jurisdiction area, and it says you can identify the correct Medicare contractor through the CMS website. It points to a Medicare contractor mismatch, not a coverage decision.

04Does a wrongly sent claim count toward timely filing?

Not for Medicare. Chapter 1, section 70.2.1, says services submitted to the wrong contractor are not considered claims until the appropriate Medicare contractor receives them. So the filing clock keeps running until the right one receives a valid claim, and a late resend can turn into a CO-29 timely filing denial.

05How is CO-109 different from CO-22?

CO-109 says the payer or contractor does not cover or process the claim and you must send it elsewhere. CO-22 says the care may be covered by another payer under coordination of benefits, so the payer order or primary payer information needs correcting.