CO-B23: Procedure Not Authorized per CLIA Proficiency Test

What Does CO-B23 Mean?

CO-B23 is the standard and nearly exclusive pairing for this code. The laboratory was not authorized under its CLIA certification to perform the billed test, and the provider must absorb the denied amount as a contractual write-off. The patient cannot be billed because CLIA compliance is a regulatory requirement that the provider is solely responsible for meeting. If the test should not have been performed at this facility, the denial is correct and the cost falls on the lab.

CARC B23 is a laboratory-specific denial tied directly to the Clinical Laboratory Improvement Amendments (CLIA) regulatory framework. When a laboratory bills for a test, the payer cross-references the procedure code against the laboratory's CLIA certificate to confirm the facility is authorized to perform that specific test. B23 fires when the payer cannot match the billed test to an authorized test on the lab's CLIA profile. This can mean the lab's certification level does not cover the test complexity, the lab failed a proficiency test for that specific analyte, or the CLIA information on the claim is incorrect.

CLIA certificates come in different levels — Certificate of Waiver, Certificate of Provider-Performed Microscopy, Certificate of Compliance (moderate complexity), and Certificate of Accreditation (high complexity). A facility with a Certificate of Waiver cannot bill for moderate or high complexity tests even if it has the equipment to perform them. Similarly, if a lab fails a proficiency test for a specific analyte, the payer may block reimbursement for that test until the lab re-establishes proficiency through successful retesting.

B23 almost exclusively pairs with Group Code CO because CLIA compliance is entirely the provider's responsibility. The patient cannot be billed for tests the laboratory was not authorized to perform. Resolution depends on the specific cause: if the CLIA number was simply entered incorrectly, correcting it resolves the claim. If the lab genuinely lacks authorization, the test should be referred to a properly certified reference laboratory. If the lab holds valid certification but the payer's records are outdated, submitting the current CLIA certificate with an appeal should clear the denial.

Common Causes

How to Resolve

Verify the laboratory's CLIA certification scope and the CLIA number on the claim, then correct any errors or refer the test to an authorized laboratory.

1. Confirm CLIA authorization Verify the lab's CLIA certificate covers the billed test. If not, the denial is correct and the test should have been referred out.
2. Correct data errors If the CLIA number was wrong on the claim, correct it and resubmit. If the payer's records are outdated, submit the current certificate.
3. Remediate proficiency issues If a proficiency test failure caused the denial, resolve the deficiency with the lab director before attempting to rebill.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-B23:

How to Prevent CO-B23

• Maintain a current, unexpired CLIA certificate and renew well before the expiration date
• Keep a reference crosswalk of CPT codes authorized under the lab's CLIA certification level
• Implement billing system edits that block submission of test codes not authorized under the facility's CLIA certificate
• Verify the correct CLIA number is populated on every laboratory claim before submission
• Monitor proficiency testing results and address deficiencies immediately to avoid billing interruptions
• Refer tests that exceed the lab's certification level to an appropriately certified reference laboratory

General Prevention

• Maintain a current CLIA certificate and renew before expiration to avoid gaps in authorization
• Keep a reference list of tests authorized under the laboratory's CLIA certification level and complexity category
• Implement billing system edits that cross-reference billed CPT codes against the lab's CLIA-authorized test list before claim submission
• Verify the correct CLIA number is populated on every laboratory claim
• Monitor CLIA proficiency testing results and address any deficiencies immediately

Also Filed As

The same CARC B23 may appear with different Group Codes:

Related Denial Codes