Claim adjustment reason code
Denial code CO-B23 meaning
CARC B23, usually seen as CO-B23: The procedure is not allowed under the lab's CLIA certificate or proficiency testing.
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- Reason code
- CARC B23
- Short name
- Not allowed under the lab's CLIA certificate
- Plain meaning
- The procedure is not allowed under the lab's CLIA certificate or proficiency testing.
- Group codes
- CO-B23: Contractual obligation. The provider absorbs the amount under its contract or the payer's rules. Do not bill the patient for it.
Plain-English summary written by Rivvi. X12 owns the CARC list and its exact wording, which is not reproduced here. Read it on the X12 CARC list (list dated November 1, 2025, checked October 23, 2026). This page does not decide how a claim is paid.
Common causes
- The lab's CLIA certificate type does not cover the test, such as a waived certificate billing a non-waived test.
What to check before resubmitting
- Check the test's CLIA category and the lab's certificate.
- Add modifier QW for a waived test when it applies.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-B23 mean?
The procedure is not allowed under the lab's CLIA certificate or proficiency testing. This is Rivvi's plain-English summary of CARC B23. X12's exact wording is on x12.org.
How do I fix CO-B23?
Check the test's CLIA category and the lab's certificate. Add modifier QW for a waived test when it applies.
Can I bill the patient for CO-B23?
With group code CO, no. CO means the provider absorbs the amount under its contract or the payer's rules.
Which group codes come with CARC B23?
Most often CO (contractual obligation). The group code, not the reason code, says who owes the amount.
What is the difference between a CARC and a RARC?
A claim adjustment reason code (CARC) says why a claim line was paid differently than billed. A remittance advice remark code (RARC) adds detail, such as which field is missing.