What to Do When Your Claim Is Denied With Code CO-109 (Claim Not Covered by This Payer)

Written By Tatiana Kadetskaya

Understanding Why Insurers Use CO-109 — and How to Appeal It

A denial code CO-109 on your Explanation of Benefits (EOB) can feel like you hit a dead end: “claim not covered by this payer / contractor.” But — just like with CO-96 — that doesn’t mean you don’t have a shot at overturning it.

Many CO-109 denials are administrative mistakes, mis-submissions, or eligibility oversights. If you catch the error and appeal properly — often with the right documentation and clear arguments — you can get those claims re-processed under the correct payer.

Here’s how to understand CO-109, when it’s correct, when it’s wrong — and what to do about it.

1. What Does CO-109 Mean?

In short: CO-109 essentially means “this payer/contractor says it isn’t responsible.”

2. Common Reasons CO-109 Denials Happen

Here are the most frequent triggers:

3. Why CO-109 Denials Deserve a Second Look — They’re Often Fixable

Just because the insurer says “wrong payer / not covered” doesn’t always mean they’re right. Here’s why some CO-109 denials are worth appealing:

  • Mistakes happen — wrong payer info, outdated coverage, or insurer confusion about which carrier covers the claim.

  • Inaccurate assumption of responsibility — maybe the claim belongs to a secondary plan, but was submitted to the primary (or vice versa), or the insurer misunderstood which payer is responsible.

  • Administration or billing errors — especially if patient policy recently changed, or provider submitted with outdated payer info.

  • Coordination of benefits / multiple insurers — if insurer failed to check benefits correctly between plans.

Because CO-109 is frequently triggered by submission to the wrong payer or outdated insurance info, a clean, well-documented appeal can get the claim reprocessed correctly.

4. What You Should Do First: Review the Denial Notice Carefully — It Holds Key Clues

Your EOB/denial notice is more than just a code. It often includes:

  • The name of the payer/contractor that denied the claim

  • The date of service / claim number / member ID / patient info

  • Possibly a remark or additional code (especially for Medicare/Medicaid or complex plans) — these can give important context about why CO-109 was applied.

If the payer listed is incorrect (or doesn’t match the patient’s current insurance), that’s your first red flag.

5. Should You Resubmit or Appeal?

Health Claim Denial 1: Claim was submitted to the wrong payer (wrong insurance ID, outdated payer, wrong contractor).

  • What to do: Correct the payer info and resubmit the claim to the correct payer/contractor

Health Claim Denial 2: Service truly shouldn’t be covered under that payer’s plan — but you believe coverage applies (e.g. under another policy)

  • What to do: Appeal the denial (especially if there’s a secondary insurer or special coverage)

Health Claim Denial 3: Denial is based on ambiguous or mistaken coverage rules (e.g. insurer misinterprets which payer applies)

  • What to do: Appeal with clear explanation and documentation

Often with CO-109 — the right move is resubmission to correct payer. But if there’s a compelling argument (dual coverage, misinterpretation of policy), an appeal makes sense.

6. How to Write a Strong Appeal (or Resubmission) for CO-109

Your appeal should follow a clear structure. Use something similar to how you handle CO-96 denials:

  1. Start by clearly identifying the claim

    • Patient name, member ID, date of birth

    • Claim number, date of service, provider name

    • Insurance plan name, payer/contractor name listed on denial, and denial code (CO-109)

  2. Explain why CO-109 is incorrect in this case

    • E.g. “This claim was submitted to Payer A, but according to Evidence of Coverage, Payer B is responsible.”

    • Or: “Attached is updated insurance documentation showing that [Insurer B] is primary/secondary payer.”

  3. Attach supporting documentation

    • Copy of denial letter/EOB

    • Policy documentation (Evidence of Coverage or Summary Plan Description)

    • Up-to-date insurance information (cards, enrollment letters)

    • If applicable — coordination of benefits forms or letters confirming which payer should cover

  4. Request correct processing under the proper payer

    • Use firm but respectful language, e.g. “Please re-process this claim under the correct payer/contractor as reflected by the attached documentation.”

    • Reference any plan rules or coverage terms if relevant

  5. Send via certified mail / return receipt if required — especially for plan appeals, to ensure there is a record.

7. When to Appeal vs. When to Simply Resubmit

  • If denial is purely administrative (wrong payer, outdated info) → resubmit.

  • If there’s valid dual coverage / complex insurance situation → appeal pointing to correct payer.

  • If the insurer mis-applied plan rules or made assumptions about which payer is responsible → appeal.

  • But if the service is truly out-of-network or excluded under both payers’ plans → appeal will likely fail; resubmission may not help.

8. Example Appeal Letter (CO-109) — Template

Re: Appeal of Denial — Claim # [claim number], DOS [date of service]

Dear Appeals Analyst,

“I am writing to appeal the denial for Claim # ______, issued on ______, which incorrectly cites denial code CO-109. Based on the plan language and the enclosed documentation, this payer is responsible for covering this claim.”

👉 This is only a preview.


The full attorney-written Appeal Letter Template includes:

  • Full argument sections for every scenario

  • Evidence checklist

  • Exact policy-language citations

  • Payer-responsibility explanations

  • Instructions for resubmission

  • Clean fill-in-the-blank structure

  • Instant download


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9. How Our CO-109 Appeal Template Helps

Because CO-109 denials often come down to administrative or payer-identification mistakes, having a ready-made, attorney-drafted appeal letter makes a big difference. A good template will:

  • Include all relevant fields (claim number, DOB, plan ID, payer name)

  • Reference plan language (Evidence of Coverage) correctly

  • Prompt you to attach key documents (EOB/denial letter, insurance info, coordination of benefits)

  • Use formal, strong appeal language that insurers take seriously

That’s exactly what your CO-109 appeal template — just like your CO-96 one — does: gives people the tools to fight denials even when the insurer seems to say “not covered.”

10. Denied for CO-109? Use the Attorney-Drafted Appeal Letter That Fixes Non-Covered Charge Denials.

A CO-109 denial can be appealed — especially when the insurer misapplies coverage rules or mislabels a covered service as “non-covered.” Instead of writing your appeal from scratch, use my Non-Covered Charges Appeal Letter Template, drafted specifically for CO-109 cases.

You’ll get:
✔ A complete attorney-written appeal
✔ Arguments that force insurers to reevaluate
✔ Evidence checklist insurers expect
✔ Step-by-step filing instructions
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You CAN Win Your Appeal

A denial letter is not the final decision. Insurance companies overturn claims every day when people submit a strong appeal.

Whether you use:

➡ The Free Appeal Guide
or
➡ The $29 Professional Appeal Template

—you can absolutely take back control and fight your denied claim with confidence.

Download Your Free Appeal Guide

Get the step-by-step instructions, evidence checklist, and sample wording you need.
Download Free Guide

Need a Full Appeal Letter Template? ($29)

Get a professionally drafted, fill-in-the-blank appeal letter tailored for medical claim denials.
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Tatiana Kadetskaya
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