Claim adjustment reason code
Denial code CO-16 meaning
CARC 16, usually seen as CO-16: The claim is missing information the payer needs, or has a billing error. The payer adds a remark code that names what is missing.
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- Reason code
- CARC 16
- Short name
- Missing or wrong information on the claim
- Plain meaning
- The claim is missing information the payer needs, or has a billing error. The payer adds a remark code that names what is missing.
- Group codes
- CO-16: 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 required field such as the NPI, the referring provider, a date, or the units is blank or invalid.
- The claim format does not meet the payer's rules.
What to check before resubmitting
- Read the remark code (RARC) on the same line. It says what to fix.
- Fix that field and send a corrected or new claim, as the payer requires.
Remark codes that often come with it
Related reason codes
Related pages
Questions
What does denial code CO-16 mean?
The claim is missing information the payer needs, or has a billing error. The payer adds a remark code that names what is missing. This is Rivvi's plain-English summary of CARC 16. X12's exact wording is on x12.org.
How do I fix CO-16?
Read the remark code (RARC) on the same line. It says what to fix. Fix that field and send a corrected or new claim, as the payer requires.
Can I bill the patient for CO-16?
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 16?
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.