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CO-8 Denial Code: Procedure Not Allowed for Provider Type

CO-8 means the procedure code is inconsistent with the provider's type or specialty, usually identified through the taxonomy code on the claim or on file with the payer. The payer does not allow that provider type to bill the service as submitted.

Quick facts

Code
CO-8 (CARC 8)
Status
Active In use since January 1, 1995; last modified July 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The normal group. The provider is responsible for the denied amount; fix the taxonomy, rendering provider, or code and resubmit.
  • PR (Patient Responsibility): Rare. It would mean the payer holds the patient responsible, which is unusual for a provider-type edit. Confirm before billing.
Official description
The procedure code is inconsistent with the provider type/specialty (taxonomy). Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-8 means

CARC 8 says the procedure code is inconsistent with the provider type or specialty (taxonomy). Payers restrict some services to certain provider types. They identify provider type from the taxonomy code reported on the claim and from the provider’s enrollment record. If the procedure does not fit that provider type, the line denies with CO-8.

This is different from a provider not being enrolled at all. With CO-8, the payer recognizes the provider but decides that, as a specialty, they may not bill this code, or that the taxonomy sent on the claim doesn’t match the one on file.

Example: a counselor enrolled under a counselor taxonomy bills a code the payer limits to physicians or psychologists. The service may be within state scope of practice, but it is outside the payer’s allowed provider types.

Common causes

  • Wrong taxonomy on the claim, such as the group’s taxonomy sent in the rendering provider loop instead of the individual’s.
  • Taxonomy on the claim differs from enrollment, often after a provider adds a specialty or changes roles.
  • Code outside the payer’s allowed provider types, for example assessment or testing codes limited to certain licensed professionals.
  • Supervising versus rendering provider confusion. Services by an unlicensed or associate-level clinician billed under their own NPI when the payer requires billing under a supervising provider, or the reverse.
  • Multi-specialty groups using one default taxonomy for all providers.

How to fix it

  1. Check the remark code (often N95) and any policy ID in the 835 REF segment.
  2. Compare the taxonomy on the claim with the taxonomy in the payer’s enrollment record and in NPPES for the rendering and billing providers.
  3. Confirm the payer’s rules for which provider types may bill the code.
  4. If the taxonomy or rendering provider was wrong, fix it and send a corrected claim with resubmission code 7 in box 22.
  5. If enrollment is wrong, update it with the payer, then request reprocessing. See provider enrollment denials.
  6. If the provider cannot bill the code, determine whether a different, appropriate code applies or whether the service should have been performed by an eligible provider. Write off what cannot be rebilled.

How to prevent it

  • Keep NPPES, payer enrollment, and your billing system in sync for every provider’s taxonomy.
  • Set taxonomy per provider, not per group, in your practice management system.
  • Maintain a list of codes restricted by provider type for each major payer.
  • Validate the rendering provider before submission. A Claims Validator check can catch taxonomy and provider-type mismatches.

Specialty notes

Behavioral health groups with mixed credentials (psychiatrists, psychologists, LCSWs, LPCs, LMFTs, and associates) see CO-8 when a code is billed under a provider type the payer does not allow for it. PT/OT groups see it when assistants’ services are billed under the wrong provider.

Remark codes that may appear with CO-8

  • N95 (This provider type/provider specialty may not bill this service.): This provider type or specialty may not bill this service.
  • N290 (Missing/incomplete/invalid rendering provider primary identifier.): Rendering provider identifier missing or invalid, often a taxonomy or NPI mismatch in the rendering loop.
  • CO-170 (Payment is denied when performed/billed by this type of provider.): Denied when performed or billed by this type of provider, a coverage rule rather than a code-level edit.
  • CO-172 (Payment is adjusted when performed/billed by a provider of this specialty.): Payment adjusted, rather than denied, because of the provider's specialty.
  • CO-185 (The rendering provider is not eligible to perform the service billed.): The rendering provider is not eligible to perform the service.
  • CO-12 (The diagnosis is inconsistent with the provider type.): The diagnosis, rather than the procedure, is inconsistent with the provider type.
  • CO-B7 (This provider was not certified/eligible to be paid for this procedure/service on this date of service.): The provider was not certified or eligible for this service on the date of service.

CO-8 FAQ

What is a taxonomy code and why does it cause CO-8?

A taxonomy code is a 10-character code that identifies a provider's type and specialty. Payers compare it with the procedure billed. If the taxonomy on the claim or in the payer's file doesn't match a provider type allowed to perform the service, the line denies.

Where is taxonomy reported on a claim?

On electronic 837P claims it goes in the provider specialty segments for the billing and rendering providers. On paper CMS-1500 forms, some payers ask for the qualifier ZZ and taxonomy in the shaded area of box 24J or box 33b. Follow payer instructions.

Can I bill the patient for CO-8?

No. The CO group code means the provider is responsible for the denied amount.