Quick Explanation
This denial indicates that the payer refused payment because the provider designated that they do not accept assignment on the claim form (Box 27 on the CMS-1500). Certain insurance plans, particularly Medicare, mandate that assignment must be accepted for specific services, rendering the claim non-covered if this option is declined.
Common Causes for CO-111
Denials with code CO-111 typically happen for the following specific reasons:
- The 'Accept Assignment' indicator (Box 27 on the CMS-1500 claim form) was erroneously marked as 'No' or left blank during claim generation.
- A non-participating Medicare provider billed for clinical diagnostic laboratory services, which legally require mandatory assignment regardless of participation status.
- The services were performed by a mid-level practitioner (such as a Nurse Practitioner or Physician Assistant) whose billing guidelines mandate the acceptance of assignment.
- The claim involved influenza, pneumococcal, or COVID-19 vaccinations billed by a non-participating physician who did not agree to accept assignment for these specific mandated services.
How to Prevent CO-111 Denials
To avoid receiving this denial in the future, implement these specific checks:
- Implement system-level edits in the practice management software to automatically default Box 27 to 'Yes' for all Medicare and government-sponsored claims.
- Create front-end scrubbing rules that reject claims before submission if Box 27 is set to 'No' while billing mandatory assignment services such as clinical laboratory codes.
- Conduct regular audits of provider credentialing files and billing templates to ensure correct alignment with participation agreements and mid-level provider billing rules.
- Train charge entry and billing staff on CMS guidelines regarding mandatory assignment rules for non-participating providers.
Appeal Letter Template for CO-111
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-111 - Not covered unless the provider accepts assignment
Dear Appeals Department,
I am writing to appeal the denial of the above-referenced claim, which was denied with code CO-111: "Not covered unless the provider accepts assignment".
We are appealing the denial under code CO-111 for the enclosed claim. Due to an administrative billing system error, Box 27 ('Accept Assignment') was incorrectly designated. Pursuant to CMS Medicare Claims Processing Manual Chapter 1, Section 30.3, we acknowledge that the billed services require mandatory assignment. We have corrected the claim to reflect that the provider accepts assignment, agreeing to accept the payer's allowed amount as payment in full. Please reprocess this corrected claim and remit payment directly to our practice in accordance with standard fee schedule guidelines.
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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