Claim adjustment reason code
Denial code CO-12 meaning
CARC 12, usually seen as CO-12: The payer does not expect this diagnosis from a provider with the type or specialty on the claim.
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- Reason code
- CARC 12
- Short name
- Diagnosis does not fit the provider type
- Plain meaning
- The payer does not expect this diagnosis from a provider with the type or specialty on the claim.
- Group codes
- CO-12: 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 rendering provider's specialty on file does not match the diagnosis billed.
What to check before resubmitting
- Check the rendering provider and the specialty on file with the payer.
Related reason codes
Related pages
Questions
What does denial code CO-12 mean?
The payer does not expect this diagnosis from a provider with the type or specialty on the claim. This is Rivvi's plain-English summary of CARC 12. X12's exact wording is on x12.org.
How do I fix CO-12?
Check the rendering provider and the specialty on file with the payer.
Can I bill the patient for CO-12?
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 12?
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.