Coding & Modifier Denials
CARC 4CARC 11CARC 199The code, modifier, or diagnosis combination did not match what the payer expected.
What it is
The pattern
A coding denial means the payer's edits rejected the code combination — an invalid modifier for the code, a diagnosis that does not support the service, or a revenue-code mismatch — rather than a coverage decision.
Why it happens
Common causes
- A modifier was appended to a code that does not accept it (or was omitted where required).
- The diagnosis does not justify the service or lacks required specificity.
- The revenue code and procedure code disagreed on the claim line.
- The code was changed at the clearinghouse to pass an edit, breaking a different edit downstream.
Prevention
Stop it before the claim goes out
- Keep a current modifier reference (what each modifier does, and which codes accept it).
- Validate the diagnosis-to-service relationship at coding time, not at denial time.
- Don't let clearinghouse 'auto-corrections' silently change codes — review them.
When it happens
What to do
Correct the code combination and resubmit as a corrected claim with frequency code 7 where the payer requires it. If the payer's edit is wrong, appeal with the coding reference (e.g., the official CPT/ICD guidance) that supports your combination.
Deeper dive
The full denial guide
The payer identified a coding issue — a mismatched or missing modifier, an inconsistent diagnosis, a revenue-code mismatch, or an unbundled service.
Open the Coding & Modifiers guide →