CO-111: Not Covered Unless Provider Accepts Assignment

What Does CO-111 Mean?

With CO (Contractual Obligation), the CARC 111 adjustment is the provider's responsibility. The payer denied or reduced payment because of certain services (such as clinical lab, Medicare Part B drugs, and DMEPOS) require mandatory assignment. The provider billed without accepting assignment for a service that requires it.. The patient is not liable for this amount.

CARC 111 indicates not covered unless provider accepts assignment. The payer determined that the service or a portion of it does not meet coverage criteria under the patient's current plan benefits or the applicable coverage rules.

Common scenarios that trigger this adjustment include: certain services (such as clinical lab, Medicare Part B drugs, and DMEPOS) require mandatory assignment. The provider billed without accepting assignment for a service that requires it.; The provider is non-participating with Medicare but billed a service that requires assignment regardless of participation status; The state Medicaid program requires assignment acceptance for the billed service, and the provider did not accept assignment. The group code paired with CARC 111 determines who bears the financial responsibility — CO places it on the provider as a contractual obligation, PR shifts it to the patient, OA indicates a coordination of benefits or other payer adjustment.

Common Causes

How to Resolve

1. Review the remittance details Examine the CO-111 adjustment and any accompanying RARC codes to identify the specific reason for the denial.
2. Identify the root cause Determine which issue applies: mandatory assignment service billed without assignment, non-participating provider billing assignment-required service, state Medicaid assignment requirement not met, among others.
3. Correct the claim Address the identified issue — update the claim data in your billing system to resolve the not covered unless provider accepts assignment problem.
4. Resubmit the corrected claim Submit the corrected claim following the payer's resubmission guidelines. Include any supporting documentation that addresses the denial reason.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-111:

How to Prevent CO-111

• Maintain a reference list of services that require mandatory assignment under Medicare and other payers
• Implement claim edits that flag mandatory assignment services before submission
• Train billing staff on which services require assignment regardless of the provider's participation status
• Consider participating provider status to avoid assignment-related denials across all services
• Review payer contracts for assignment requirements specific to the services your practice provides

Also Filed As

The same CARC 111 may appear with different Group Codes:

Related Denial Codes