Denial Code CO-4: Description, Meaning and How to Fix It
A modifier is missing or wrong for the procedure billed.
Official description
The procedure code is inconsistent with the modifier used, or a required modifier is missing.
Common cause
A required modifier was omitted, or an incorrect modifier was appended.
How to fix it
Add or correct the modifier per payer and CPT rules, then resubmit.
Related denial codes
- CO-11: The diagnosis code does not match or support the procedure billed.
- CO-146: The diagnosis code was not valid for that date of service.
- CO-6: The procedure billed does not fit the patient's age per payer edits.
- M76: The diagnosis is missing, incomplete, or invalid on the claim.
- CO-45: The amount billed is higher than the payer's contracted (allowed) rate. The difference is a contractual write-off, not a patient balance.
- CO-16: The claim is missing required information or has an error. It is almost always paired with a RARC that names the specific missing field.