CO-29 Denial — How to Appeal for Behavioral Health
CO-29 (timely filing limit expired) 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-29 means
The payer says the claim was submitted after their filing deadline. Most commercial payers require claims within 90–365 days of the date of service; Medicaid and Medicare have their own windows.
Appeal strategy for CO-29
Appeal with documented proof that the claim was submitted on time — clearinghouse submission reports with timestamps are ideal. If late submission was caused by payer error (e.g. incorrect enrollment, address change not processed), document the cause and cite any applicable exceptions. For government programs, cite the exact regulatory exception you are invoking.
CPT codes commonly denied with CO-29
Appeal CO-29 by payer
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Generate my appeal letter →Frequently asked questions about CO-29
What does CO-29 mean on a behavioral health claim?
The payer says the claim was submitted after their filing deadline. Most commercial payers require claims within 90–365 days of the date of service; Medicaid and Medicare have their own windows.
How do I appeal a CO-29 denial?
Appeal with documented proof that the claim was submitted on time — clearinghouse submission reports with timestamps are ideal. If late submission was caused by payer error (e.g. incorrect enrollment, address change not processed), document the cause and cite any applicable exceptions. For government programs, cite the exact regulatory exception you are invoking.
Does MHPAEA apply to CO-29 denials?
CO-29 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-29 denial?
All major commercial payers — Aetna, Cigna, Anthem, UnitedHealthcare, Humana, and BCBS plans — use CO-29. 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.