Guide · After a decision
What does CO-50 mean on my letter?
A short code many people see. Here's what it says and what you can do about it.
You open the letter and there it is: CO-50. It looks like a secret. It isn't. It's a short label that explains why a charge was not paid.
What it usually means
CO-50 is commonly used when the plan decided the service was "not medically necessary" under its rules. "CO" usually means the provider, not you, is the one asked to cover that amount. Your own letter and your plan explain the rest.
Where to check it
Your plan describes what it treats as medically necessary and how it decides. We find that section in the filed forms and show the page, so you can read it yourself.
What you can do next
Check the date on the letter. It tells you how long you have to ask for another look. Gather the papers your provider can share. Then decide whether to ask. You send it yourself.
What we can't tell you
Whether your insurer will change its mind. They decide. We show what the document says.