RemitBench/Denial codes/CO-109

CO-109 denial code

Code 109 is the clearest instruction in the whole code list. This payer is not the right one, and the second sentence of the official description tells you exactly what to do.

The code list's own wording: Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor.

What it means: The payer you billed has no responsibility for this claim. It might be the wrong company, the wrong plan within that company, the wrong regional contractor, or the wrong line of business.
Who owes the money: A different payer Not the patient, until you have found out who the right payer is and whether they cover it. A 109 is not a coverage decision, so it cannot make anything the patient's balance.
Is appealing worth it: No. There is no decision to appeal. The payer has told you it is not involved. Send the claim to the one that is.

This is one of the most write-off-in-error codes in the list. A 109 looks like a denial and reads like one, and the money is nearly always recoverable, because somebody covers this patient. Writing it off is giving up on a claim that has not been adjudicated anywhere.

Watch the filing clock at the real payer. Time spent working a 109 counts against the deadline at the payer who has not seen the claim yet. This is the single most common route from a fixable routing problem to an unfixable CO-29.

Why the payer sent it

The patient changed plans and gave you the old card.
The claim went to the medical plan when it belonged to the dental plan, or the reverse.
The patient is on a Medicare Advantage plan and the claim went to traditional Medicare, which is a very common version of this.
The right company was billed and the wrong plan or line of business within it.
A regional contractor boundary, where the claim needed a different one.
Another carrier is liable because of an injury, which is CO-19 territory.

Remark codes you will see with it

Remark code	What it adds
N418	The claim was misrouted. Confirms the reading directly.
MA130	Unprocessable claim, no appeal rights. Resubmit rather than appeal.
N130	Read the plan document. Its own page.

Remark code

What it adds

N418

The claim was misrouted. Confirms the reading directly.

MA130

Unprocessable claim, no appeal rights. Resubmit rather than appeal.

N130

Read the plan document. Its own page.

Read the letters in front of the 109

CO-109: Contractual obligation. The common pairing, and it should never stay a write-off.
OA-109: Other adjustment. Points the money elsewhere rather than at either side.
PI-109: Payer initiated. Not the patient's money.
PR-109: Patient responsibility. Wrong on the face of it. A patient cannot owe your fee because a claim went to the wrong company.

What to do next

Run an eligibility check for the date of service

This answers the real question directly and faster than a phone call: who covered this patient that day.
If it names another plan: you have your answer. Send the claim there today, not next week.
Ask the patient for their current card

The most common cause is the simplest. Ask for a photograph of the front and back, which saves a second call about the payer address.
Check whether it is a Medicare Advantage claim

A patient on an Advantage plan is not billed to traditional Medicare, and the patient often does not realise their plan is one. This single check resolves a large share of these in practices that see older patients.
Send it to the right payer and watch that deadline

The clock at the correct payer has been running since the date of service. Treat a 109 as urgent rather than routine, because it is the one denial where delay destroys the claim.

Codes that get mixed up with 109

Code	How it differs from 109
22	Another payer may be primary. Right payer, wrong order. This one is the wrong payer entirely. See CO-22.
31	The payer cannot identify the patient. It may still be the right payer with wrong details. See CO-31.
27	Coverage had ended. The right payer, a date outside the coverage. See PR-27.
26	Coverage had not started. See PR-26.
19	A work injury, so a compensation carrier is liable. See CO-19.

Four codes describe four different failures to reach the right plan: wrong payer, wrong order, wrong details, wrong dates. The fix is different for each, and the letters do not tell you which one you have.

Code 109 in dental

Dental practices meet this more than most, because dental benefits are often administered by a different company from the medical plan, and patients carry one card rather than two.

The medical card in the wallet

A patient hands over the card they have. The dental benefit sits with another administrator, under another member number, and the claim goes to a payer with no dental responsibility at all. Asking specifically for the dental card at check in prevents most of these.

Medical cross coded claims go the other way

When a dental office bills medical for a surgical extraction or a sleep appliance, a 109 can mean the medical payer thinks it belongs on the dental side. Read it as a routing instruction rather than a coverage refusal, and be ready to argue which side a crossover procedure belongs on.

Questions people ask about CO-109

Can I bill the patient for a CO-109?

No. The payer did not decide anything about coverage, it said it is not the right payer. The service may be fully covered by the correct plan, and nothing can be the patient's responsibility until a payer that is actually responsible has adjudicated the claim.

What is the difference between CO-109 and CO-22?

A 22 means the right payers were involved in the wrong order: bill the primary first, then come back. A 109 means this payer is not involved at all: send the claim somewhere else entirely.

Why do I get CO-109 from Medicare?

Most often because the patient is enrolled in a Medicare Advantage plan, which pays their claims instead of traditional Medicare. Patients frequently do not know this about their own plan, so an eligibility check for the date of service is more reliable than asking.

Related codes

Back to all denial codes

RemitBench reads dental EOB PDFs and turns them into posting-ready lines, in your browser, with no upload. It does not read medical remittances today.

Open the app

Opens your mail app with the message written. Nothing is sent from this page.