CO-4Contractual Adjustment
Missing or incorrect modifier
What this code means
Your claim was missing a code that tells the insurer more detail about how or where a service was performed. Without it, the claim cannot be processed.
What to do next
Ask your provider to review the claim for missing modifiers and resubmit with the correct modifier attached. This is a provider-side fix, not an appeal.
Recommended tool
Bill Advantage can analyze your denial and generate a ready-to-send appeal or dispute letter in minutes.
Open Denial Letter Translator