CO-B20: Service Furnished by Another Provider

What Does CO-B20 Mean?

CO-B20 designates the denied amount as a contractual write-off because the payer determined another provider already furnished the service. The provider cannot bill the patient for the denied amount. This is the standard pairing and indicates the payer paid the other provider for the same service. The denial is correct if the other provider genuinely performed the work; it requires correction if the billing attribution was wrong or the services were shared.

CARC B20 fires when the payer's records indicate that the billed procedure or service was already provided — in whole or in part — by a different healthcare provider. The payer is protecting against double payment for the same service. This code is fundamentally about provider attribution: who actually performed the service, and is there a legitimate claim from each party involved?

The most common trigger is a billing coordination failure between collaborating providers. When a primary care physician refers a patient to a specialist who performs a procedure, both providers may inadvertently bill for the same service or components of it. Similarly, when a practice outsources laboratory work, imaging, or technical components to an external facility, both the referring practice and the performing facility may submit claims. B20 catches these overlaps and denies the claim from the provider the payer considers duplicative.

B20 pairs primarily with CO, making the denied amount a provider write-off. If the other provider legitimately performed the service, the denial is correct — you cannot bill for work someone else did. However, if the services were shared (co-surgery, team surgery, or split technical/professional components), the denial may be incorrect and should be resolved by adding appropriate modifiers. Modifier 62 for two-surgeon scenarios, modifiers 80-82 for assistant surgeon roles, and TC/26 modifiers for technical/professional component splits all help the payer distinguish legitimate shared billing from duplicate claims.

Common Causes

How to Resolve

Determine whether the service was genuinely furnished by another provider, coordinate billing with the other provider, and resubmit with appropriate modifiers if the service was shared or independently performed.

1. Verify the other provider's claim Confirm what the other provider billed and whether their claim accurately reflects who performed the service.
2. Correct attribution if needed If your provider performed the service, resubmit with operative notes and documentation. Use modifier 62, 80-82, or TC/26 as appropriate.
3. Accept if the denial is correct If the other provider did perform the service, accept the denial and void the duplicate claim.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-B20:

How to Prevent CO-B20

• Coordinate billing with referring providers, specialists, and facilities before submitting claims for shared or outsourced services
• Establish clear billing protocols that define which provider bills for which component when services are collaborative
• Use appropriate modifiers for co-surgery, assistant surgeon, and technical/professional component splits
• Document clearly in the medical record which provider performed each component of a shared service

General Prevention

• Coordinate billing with referring providers and specialists before submitting claims for shared or outsourced services
• Implement clear billing protocols that define which provider bills when services are performed collaboratively
• Use appropriate modifiers (62, 66, or 80-82) to indicate shared surgical or assistant services
• Verify with the payer whether the service requires a specific designated provider before rendering and billing
• Document clearly in the medical record which provider performed each component of a service

Also Filed As

The same CARC B20 may appear with different Group Codes:

Related Denial Codes