Claim adjustment reason code
Denial code CO-146 meaning
CARC 146, usually seen as CO-146: The diagnosis code was not valid on the date of service.
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- Reason code
- CARC 146
- Short name
- Diagnosis invalid for the date of service
- Plain meaning
- The diagnosis code was not valid on the date of service.
- Group codes
- CO-146: 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 or not-yet-effective ICD-10-CM code was used.
- A header code was billed instead of a billable code.
What to check before resubmitting
- Check the code against the ICD-10-CM release for the date of service. Codes change each October 1.
- Use a billable code at full specificity.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-146 mean?
The diagnosis code was not valid on the date of service. This is Rivvi's plain-English summary of CARC 146. X12's exact wording is on x12.org.
How do I fix CO-146?
Check the code against the ICD-10-CM release for the date of service. Codes change each October 1. Use a billable code at full specificity.
Can I bill the patient for CO-146?
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 146?
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.