CO-11 — Diagnosis Inconsistent with Procedure

CO-11 means the ICD-10 diagnosis code does not medically justify the CPT code billed. In behavioral health, this arises when the diagnosis is too unspecific (e.g. using F32 instead of F32.1) or when the diagnosis category does not match the service type. The fix is usually a corrected claim with a more specific ICD-10 code plus a brief clinical summary — not a formal appeal.