Claim adjustment reason code
Denial code CO-181 meaning
CARC 181, usually seen as CO-181: The procedure code was not valid on the date of service.
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- Reason code
- CARC 181
- Short name
- Procedure code invalid on the date of service
- Plain meaning
- The procedure code was not valid on the date of service.
- Group codes
- CO-181: 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
- A deleted code, or a code not yet effective, was billed.
- A typo created a code that does not exist.
What to check before resubmitting
- Check the code against the HCPCS or CPT release for the date of service.
- Use the replacement code and resubmit.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-181 mean?
The procedure code was not valid on the date of service. This is Rivvi's plain-English summary of CARC 181. X12's exact wording is on x12.org.
How do I fix CO-181?
Check the code against the HCPCS or CPT release for the date of service. Use the replacement code and resubmit.
Can I bill the patient for CO-181?
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 181?
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.