Claim adjustment reason code
Denial code CO-26 meaning
CARC 26, usually seen as CO-26: The date of service is before the patient's coverage began.
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- Reason code
- CARC 26
- Short name
- Service before coverage started
- Plain meaning
- The date of service is before the patient's coverage began.
- Group codes
- CO-26: Contractual obligation. The provider absorbs the amount under its contract or the payer's rules. Do not bill the patient for it. PR-26: Patient responsibility. The patient, or a secondary payer, may owe the amount.
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 plan's effective date is after the date of service.
- The patient had different coverage on that date.
What to check before resubmitting
- Check eligibility for the date of service.
- Bill the plan that covered the patient on that date.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-26 mean?
The date of service is before the patient's coverage began. This is Rivvi's plain-English summary of CARC 26. X12's exact wording is on x12.org.
How do I fix CO-26?
Check eligibility for the date of service. Bill the plan that covered the patient on that date.
Can I bill the patient for CO-26?
When it comes with group code PR, the patient or a secondary payer may owe the amount. When it comes with CO, the provider writes it off.
Which group codes come with CARC 26?
Most often CO (contractual obligation) or PR (patient responsibility). 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.