How to Appeal a Prior Authorization Denial (CO-11)
Claim denied for missing prior authorization (CO-11)? Understand what happened, your rights, and how to write a compelling appeal letter to get your claim paid.
What does CO-11 mean?
A CO-11 denial means the service you received required prior authorization (pre-approval) from your insurer before it was performed, and either authorization was not obtained, was obtained incorrectly, or the authorization that was obtained did not match the services actually rendered. CO-11 is one of the top five most common denial codes.
Why insurers issue CO-11 denials
Insurers require prior authorization for expensive procedures, brand-name medications, specialist referrals, and elective surgeries as a cost-control mechanism. When authorization is missing, whether because the provider forgot, the emergency made it impossible, or the authorization code doesn't match, the insurer denies the claim entirely, leaving the patient with the full bill.
Appeal strategy
If the service was an emergency, cite state and federal law (including the ACA and ERISA) that prohibit insurers from requiring prior authorization for emergency services. If the omission was a provider error, request that the provider file a retroactive authorization and document it. If authorization was obtained but coded incorrectly, request a concurrent review and supply the original authorization documentation.