Appealing an Aetna CO-167 Denial
An Aetna CO-167 denial (diagnosis not covered) is one of the most common claim rejections behavioral health therapists face. This guide explains exactly what caused the denial and the most effective appeal strategy for behavioral health practices.
What this denial means
The payer is saying the diagnosis code you submitted is not covered under the patient's plan. In behavioral health, this often surfaces as an exclusion for certain mental health diagnoses (e.g. adjustment disorder, V-codes, or substance use) that would not be excluded if they were medical diagnoses.
MHPAEA Mental Health Parity Argument
Selectively excluding mental health diagnoses that would be covered if they were medical diagnoses is a non-quantitative treatment limitation (NQTL) under MHPAEA — the payer cannot exclude a behavioral diagnosis without a comparable exclusion for similar medical diagnoses. Demand the CAA 2021 § 203 NQTL comparative analysis in writing; that statutory disclosure duty applies regardless of the 2025 federal non-enforcement of the 2024 Final Rule.
Request Aetna's written Non-Quantitative Treatment Limitation (NQTL) comparative analysis. They are required to provide it under the MHPAEA Enforcement Final Rule (2024).
Your appeal strategy
Review the plan's covered diagnoses list and compare the mental health exclusions against any exclusions applied to analogous medical diagnoses. If the exclusion is diagnosis-specific for mental health only, invoke MHPAEA: excluding a mental health diagnosis that would be covered if it were a medical diagnosis violates parity. Also verify whether the ACA essential health benefit (EHB) mandate covers this diagnosis.
What Aetna requires
P.O. Box 14463
Lexington, KY 40512
30 calendar days (Level-1 appeal)
60 days from Level-1 denial
1-860-754-2985
Aetna publishes MHPAEA comparative analyses on request; behavioral health benefits are administered through Aetna Behavioral Health. Document parity violation in detail — Aetna's internal process requires a specific MHPAEA flag in the appeal routing system.
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Generate my appeal letter →Frequently asked questions
How long does Aetna have to respond to a CO-167 appeal?
Under federal regulations and most state prompt-payment laws, Aetna must respond to a Level-1 internal appeal within 30 calendar days. If you receive an adverse determination, you typically have 60 calendar days from the date of the Level-1 denial to request external review. Send the appeal via certified mail or through the payer's portal and keep documentation of the submission date.
Does MHPAEA apply to CO-167 denials?
Yes. Selectively excluding mental health diagnoses that would be covered if they were medical diagnoses is a non-quantitative treatment limitation (NQTL) under MHPAEA — the payer cannot exclude a behavioral diagnosis without a comparable exclusion for similar medical diagnoses. Demand the CAA 2021 § 203 NQTL comparative analysis in writing; that statutory disclosure duty applies regardless of the 2025 federal non-enforcement of the 2024 Final Rule. When filing a CO-167 appeal against Aetna, request their written comparative analysis for mental health vs. medical/surgical benefits under 29 CFR § 2590.712. Aetna publishes MHPAEA comparative analyses on request; behavioral health benefits are administered through Aetna Behavioral Health. Document parity violation in detail — Aetna's internal process requires a specific MHPAEA flag in the appeal routing system.
Can I appeal a CO-167 denial more than once?
Yes. Most payers, including Aetna, allow at least two levels of internal appeal (Level-1 and Level-2 or "expedited" review). After exhausting internal appeals, you have the right to request an Independent Medical Review (IMR) or external review through your state insurance commissioner. Keep copies of every appeal, submission confirmation, and payer response.
What documentation do I need to appeal a CO-167 denial from Aetna?
At minimum: the original Explanation of Benefits (EOB) or Remittance Advice (RA) showing the CO-167 denial, the original claim details (CPT code, date of service, NPI, charge amount), and any clinical documentation supporting medical necessity. Because this code has parity implications, also include a written request for Aetna's NQTL comparative analysis under MHPAEA. Submit everything in one packet with a cover letter citing the specific denial code, the date of service, and the claim number.