Denial code · Contractual Obligation (CO)
CO-4 denial code
The service code and the extra code that adds detail to it do not match.
What the code means
Official meaning: The procedure code is inconsistent with the modifier used.
In plain words: The service code and the extra code that adds detail to it do not match.
The usual fix
Check the payer's list for the right extra code for that service, fix it, and send the claim again corrected.
This is general information, not advice on a specific claim.
Learn on the job
Learn on the job with real denied claims.
Working denied claims is the medical claims desk's daily work. Read a code, find what is missing, fix the claim, or write the appeal.