CO-15 Denial — How to Appeal for Behavioral Health
CO-15 (authorization number missing or invalid) is one of the most common insurance denial codes behavioral health therapists encounter. This guide explains what triggered the denial and the most effective appeal strategy across all major payers.
What CO-15 means
The payer cannot match the authorization number on your claim to a valid prior authorization in their system. This is different from CO-197 (no auth obtained) — here the auth may exist but the number is wrong, missing from the claim form, or expired.
Appeal strategy for CO-15
Pull the authorization number from your records and verify it matches exactly what appears on the claim. If it does, provide the authorization confirmation document with your appeal. If the payer issued the auth but cannot find it, request escalation to the authorization department and document all contact attempts.
CPT codes commonly denied with CO-15
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What does CO-15 mean on a behavioral health claim?
The payer cannot match the authorization number on your claim to a valid prior authorization in their system. This is different from CO-197 (no auth obtained) — here the auth may exist but the number is wrong, missing from the claim form, or expired.
How do I appeal a CO-15 denial?
Pull the authorization number from your records and verify it matches exactly what appears on the claim. If it does, provide the authorization confirmation document with your appeal. If the payer issued the auth but cannot find it, request escalation to the authorization department and document all contact attempts.
Does MHPAEA apply to CO-15 denials?
CO-15 is a general adjudication code that typically applies equally to all claim types. MHPAEA may still be relevant if the payer applies the underlying rule differently to mental health services than to comparable medical/surgical services.
Which insurers most commonly issue a CO-15 denial?
All major commercial payers — Aetna, Cigna, Anthem, UnitedHealthcare, Humana, and BCBS plans — use CO-15. Government programs (Medicare, Medicaid, TRICARE) also issue this code. The appeal strategy is similar across payers, but deadlines and submission addresses vary. Select your payer from the list below for payer-specific instructions.