CO-B20 denial code
Procedure was partially or fully furnished by another provider
How to fix it
Confirm what your provider performed and bill only that portion with the appropriate modifier.
How to prevent it
Coordinate billing where care is shared between providers to avoid overlapping claims.
In practice
Two surgeons each perform a distinct part of a complex procedure. Both bill the full procedure code, and the second claim returns CO-B20.
The payer has established that the service was shared, and it will not pay two providers for the same complete procedure. What each performed has to be reported as what each performed.
Co-surgery, team surgery and split billing each have their own modifiers, and applying the right one lets both providers be paid for their portion. Billing the whole code twice will not.
What sits behind it
The mechanisms are distinct and the modifier choice follows the arrangement. Modifier 62 reports co-surgeons each performing a distinct part of one procedure, 66 reports a surgical team, and 80 through 82 report assistant roles, each paying differently.
Global period splitting is a separate case with its own modifiers. Where one provider performs the surgery and another provides the postoperative care, modifiers 54, 55 and 56 divide the global package between them, and using them prevents exactly this denial.
Coordination between practices is what makes any of this work. Where two groups bill independently without agreeing who reports what, the second claim to arrive denies regardless of which provider did more, so the conversation belongs before submission.
Related codes
Terms used here — Modifier · NCCI Edits · CPT Code
How we handle it — Medical Coding · Denial Management · Claims Management
Primary sources
The rules behind CO-B20, at the bodies that publish them.
- NCCI Policy Manual for Medicare Services (opens in a new tab)
Centers for Medicare & Medicaid Services — The reasoning behind the edits, chapter by chapter. Where the edit files tell you two codes conflict, this explains why — which is what an appeal has to address.
- National Correct Coding Initiative (NCCI) edits (opens in a new tab)
Centers for Medicare & Medicaid Services — The procedure-to-procedure and medically-unlikely edits behind most bundling denials. Checking these before submission prevents the denial entirely.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-B20
By reporting the arrangement accurately with the right modifier — 62 for co-surgeons each performing a distinct part, 66 for a surgical team, and 80 through 82 for assistant roles. Billing the complete code twice produces this denial whatever the actual work.
That uses modifiers 54, 55 and 56 to divide the global package between the surgeon and the provider furnishing postoperative care. Applying them correctly prevents this denial and pays each provider for what they actually delivered.
The second claim denies regardless of which provider did more, which is why coordination has to happen before submission. Two groups billing independently without agreeing who reports what will produce this denial every time.
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