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CO-125 Denial Code (Deactivated): Submission/Billing Error

CO-125 meant the claim had submission or billing errors, with a remark code required to say what was wrong. X12 deactivated it without naming a successor; CARC 16, which also requires a remark code, covers the same ground today.

X12 deactivated CARC125 on November 1, 2013. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Code: CO-125 (CARC 125)
Status: Deactivated StoppedNovember 1, 2013 (in use since January 1, 1995).
Code set: Claim Adjustment Reason Codes (CARC)
Group codes: CO (Contractual Obligation): Billing errors are the provider's responsibility to fix; the patient was not billed.
Official description: Submission/billing error(s). At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.)
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What CO-125 meant

CARC 125 was a general “something is wrong with how this claim was submitted” code. The claim might have had an invalid identifier, a missing date, a formatting problem, or another data error. The adjustment code itself was generic; the remark code attached to it pointed to the specific field.

What replaced it

X12 did not name a replacement. The active code covering the same problem is CO-16, used for claims that lack information or have submission or billing errors, and it also requires a remark code. When the fix is documentation rather than data, payers may use CO-252. A code that was not valid on the service date gets CO-181.

If you still see CO-125

It may appear on older denials in your A/R history. Read the remark code, correct the field it identifies, and resubmit as a corrected or replacement claim according to the payer’s rules. Since these errors tend to repeat, add the fix to your claim scrubber or charge entry checks so the same mistake does not reach the payer again.

CO-16 (Claim/service lacks information or has submission/billing error(s).): Claim lacks information or has submission or billing errors; the active code for this situation.
CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment or other documentation is required to adjudicate the claim.
CO-181 (Procedure code was invalid on the date of service.): Procedure code was invalid on the date of service.

CO-125 FAQ

How is CO-125 different from CO-16?

They overlapped heavily. CARC 16 covers claims lacking information or having submission or billing errors, so once it was broadened, a separate code 125 was no longer needed.

Where do I find what the error was?

In the remark code sent with it. CO-125 always required at least one non-alert remark code that identified the problem field.

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