Claim adjustment reason code
Denial code CO-B12 meaning
CARC B12, usually seen as CO-B12: The services are not documented in the patient's medical record.
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- Reason code
- CARC B12
- Short name
- Not documented in the record
- Plain meaning
- The services are not documented in the patient's medical record.
- Group codes
- CO-B12: 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 record does not show the service billed.
What to check before resubmitting
- Check the record. Appeal with documentation, or remove the line.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-B12 mean?
The services are not documented in the patient's medical record. This is Rivvi's plain-English summary of CARC B12. X12's exact wording is on x12.org.
How do I fix CO-B12?
Check the record. Appeal with documentation, or remove the line.
Can I bill the patient for CO-B12?
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 B12?
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.