Appealing an Aetna OA-23 Denial
An Aetna OA-23 denial (prior payer adjustment (coordination of benefits)) 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
This is a coordination-of-benefits code, not a prior-authorization denial. It means the client has more than one insurance plan, and this payer reduced or adjusted the payment based on what the primary payer already paid or adjusted. It shows up when the payer is the secondary plan on a claim, not when they are questioning whether authorization was obtained.
Your appeal strategy
Request the payer's coordination-of-benefits breakdown showing exactly how the primary payer's EOB or adjustment was applied to this claim. If the client has no other coverage on file, or the COB calculation looks wrong, submit the primary payer's EOB and dispute the specific numbers with the payer.
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.
Generate your Aetna OA-23 appeal letter
Therapists get 5 free letters every month. Appealing your own denial? It's $19 per letter, one-time, no subscription. No credit card needed to start.
Generate my appeal letter →Frequently asked questions
How long does Aetna have to respond to a OA-23 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 OA-23 denials?
OA-23 denials are not directly tied to mental health parity protections in most cases — this code is a general adjudication rule that applies equally to all claim types. MHPAEA may still be relevant if the underlying reason for the denial differs for mental health vs. medical/surgical services.
Can I appeal a OA-23 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). Keep copies of every appeal, submission confirmation, and payer response. After exhausting internal appeals, fully-insured commercial and ACA marketplace plans give you the right to request an Independent Medical Review (IMR) or external review through your state Department of Insurance. Self-funded employer (ERISA) plans instead use the federal external-review process overseen by the U.S. Department of Labor's Employee Benefits Security Administration (EBSA) — not the state insurance commissioner. Check your plan documents or Summary Plan Description to confirm which applies.
What documentation do I need to appeal a OA-23 denial from Aetna?
At minimum: the original Explanation of Benefits (EOB) or Remittance Advice (RA) showing the OA-23 denial, the original claim details (CPT code, date of service, NPI, charge amount), and any clinical documentation supporting medical necessity. Submit everything in one packet with a cover letter citing the specific denial code, the date of service, and the claim number.