Quick Explanation
Denial code CO-99 indicates that the insurance carrier has suspended or denied the claim because they require updated Coordination of Benefits (COB) information to determine which insurer is primary and which is secondary. This usually occurs when the payer suspects the patient has dual health coverage, requiring the patient or provider to verify the order of benefits before the claim can be processed.
Common Causes for CO-99
Denials with code CO-99 typically happen for the following specific reasons:
- The patient has multiple active insurance policies but has not completed the payer's annual COB verification questionnaire.
- The claim was submitted to a secondary insurance payer without the primary insurer's Explanation of Benefits (EOB) attached.
- The patient's coverage status recently changed due to a new job, marriage, or divorce, and the payer's database has outdated coordination details.
- The billing office did not populate the required COB fields (such as Loop 2320 on electronic 837 claims) when submitting a multi-payer claim.
How to Prevent CO-99 Denials
To avoid receiving this denial in the future, implement these specific checks:
- Establish a robust pre-registration workflow to verify the patient's primary and secondary insurance details during every visit.
- Promptly instruct patients at check-in to contact their insurance carrier to update their coordination of benefits if dual coverage is identified.
- Always submit the primary payer's remittance advice or EOB alongside the secondary claim to satisfy COB documentation requirements.
- Utilize real-time eligibility (RTE) verification transactions to identify other active policies before submitting claims.
Appeal Letter Template for CO-99
If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.
[Your Practice Header]
[Date]
[Payer Name]
[Appeals Department Address]
RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: CO-99 - Coordination of Benefits (COB) information was not provided
Dear Appeals Department,
I am writing to appeal the denial of the above-referenced claim, which was denied with code CO-99: "Coordination of Benefits (COB) information was not provided".
We are writing to appeal the denial of this claim under code CO-99 regarding Coordination of Benefits (COB). Our records indicate that the patient's coverage was active on the date of service, and we have attached the completed coordination of benefits questionnaire along with the primary insurance Explanation of Benefits (EOB) confirming the correct order of liability. In accordance with standard coordination of benefits guidelines established under the National Association of Insurance Commissioners (NAIC) and CMS regulations, the enclosed documentation supports the payment of this claim. We respectfully request that you update the member's eligibility file and reprocess this claim for payment.
Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].
We respectfully request that you reprocess this claim for payment.
Sincerely,
[Your Name]
[Title]
[Practice Name]
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