CO-16 Denial — How to Appeal for Behavioral Health
CO-16 (missing or incomplete information) 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-16 means
The payer says your claim is missing information required to process it. You should receive a remark code (RARC) with this denial specifying exactly what is missing — look for an N-code or M-code on the same line of the RA.
Appeal strategy for CO-16
Identify the specific remark code that accompanies CO-16. Resubmit the claim with the missing element (NPI, taxonomy code, rendering provider, place of service, etc.). If the claim data was complete and the denial is in error, appeal with documentation proving each required field was present.
CPT codes commonly denied with CO-16
Appeal CO-16 by payer
Select your payer for appeal address, deadline, and payer-specific MHPAEA notes.
Generate your CO-16 appeal letter in 60 seconds
First 5 letters free. No credit card. MHPAEA arguments included when applicable.
Generate my appeal letter →Frequently asked questions about CO-16
What does CO-16 mean on a behavioral health claim?
The payer says your claim is missing information required to process it. You should receive a remark code (RARC) with this denial specifying exactly what is missing — look for an N-code or M-code on the same line of the RA.
How do I appeal a CO-16 denial?
Identify the specific remark code that accompanies CO-16. Resubmit the claim with the missing element (NPI, taxonomy code, rendering provider, place of service, etc.). If the claim data was complete and the denial is in error, appeal with documentation proving each required field was present.
Does MHPAEA apply to CO-16 denials?
CO-16 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-16 denial?
All major commercial payers — Aetna, Cigna, Anthem, UnitedHealthcare, Humana, and BCBS plans — use CO-16. 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.