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CO-B6 Denial Code (Deactivated): Provider Type/Specialty

CO-B6 meant payment was adjusted because of who performed or billed the service: the provider type, the provider type in that facility, or the provider's specialty. X12 deactivated it without naming a successor; codes 170, 171, and 172 now cover these cases.

X12 deactivated CARCB6 on February 1, 2006. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Quick facts

Code
CO-B6 (CARC B6)
Status
Deactivated StoppedFebruary 1, 2006 (in use since January 1, 1995).
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The adjustment stemmed from provider or facility rules, so it was not billed to the patient.
Official description
This payment is adjusted when performed/billed by this type of provider, by this type of provider in this type of facility, or by a provider of this specialty.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-B6 meant

CARC B6 said the payment was adjusted, which could mean reduced or denied, because of the kind of provider involved. The issue might be the provider type, the combination of provider type and facility, or the provider’s specialty. All three were rolled into one code.

What replaced it

X12 did not name a replacement, but it later added three narrower codes that line up with the three parts:

  • CO-170 for provider type.
  • CO-171 for provider type in a particular facility type.
  • CO-172 for provider specialty.

When the procedure code does not fit the taxonomy reported, payers use CO-8.

If you still see CO-B6

It is a legacy code. If you are working a historical claim, compare the rendering provider’s taxonomy and enrollment details with the payer’s billing policy for that service. A wrong taxonomy is easy to correct and resubmit. A true restriction on provider type is usually final for that claim, but it may be worth billing under an eligible supervising provider in future where the payer’s rules allow it.

  • CO-170 (Payment is denied when performed/billed by this type of provider.): Payment is denied when performed or billed by this type of provider.
  • CO-171 (Payment is denied when performed/billed by this type of provider in this type of facility.): Payment is denied when performed or billed by this type of provider in this type of facility.
  • CO-172 (Payment is adjusted when performed/billed by a provider of this specialty.): Payment is adjusted when performed or billed by a provider of this specialty.
  • CO-8 (The procedure code is inconsistent with the provider type/specialty (taxonomy).): The procedure code is inconsistent with the provider type or specialty (taxonomy).

CO-B6 FAQ

What typically causes a provider-type adjustment?

A payer may pay certain services only when billed by specific license types, reduce payment for some clinician types, or restrict services in certain facility settings. Incorrect taxonomy codes on the claim can also cause it.

How do I fix one?

Check that the rendering provider's taxonomy and specialty on the claim match the payer's enrollment records, and review the payer's policy on which provider types may bill the service.