On your explanation of benefits or remittance, CO-15 means: authorization number missing or invalid.
Is there an overturn-rate benchmark for this code?
Honest answer: no. State external-review programs are limited by statute to clinical-necessity disputes, so administrative and financial denial codes like this one never reach external review and no published overturn rate exists. Anyone quoting one for this code is inventing it.
What to do next
This code is generally appealable. Internal appeal deadlines are typically 180 days from the denial.
If your denial arrived near-instantly or names no reviewing physician, several states now bar algorithm-only medical-necessity denials — ask in writing who reviewed the claim.
Always request an itemized bill and keep everything in writing.
Now turn the number into a dispute. Knowing your percentile is step one; the letter that cites it, the visit-code check, and the deadlines are the rest. Medigami builds those from your actual bill — medigami.com