Aetna Insurance Appeal Guide
A complete reference for behavioral health therapists appealing an Aetna denial. Every common CARC code, the correct appeal address, MHPAEA parity arguments, and response deadlines — all in one place.
Aetna appeal details
P.O. Box 14463
Lexington, KY 40512
30 calendar days
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.
Most common Aetna denial codes
All Aetna denial code appeal guides
Select a code to see the denial explanation, appeal strategy, MHPAEA arguments, and a direct link to generate your appeal letter.
| Code | Denial reason | Guide |
|---|---|---|
| CO-4 | Modifier Inconsistent with Procedure | Appeal guide → |
| CO-11 | Diagnosis Inconsistent with Procedure | Appeal guide → |
| CO-15 | Authorization Number Missing or Invalid | Appeal guide → |
| CO-16 | Missing or Incomplete Information | Appeal guide → |
| CO-18 | Duplicate Claim | Appeal guide → |
| CO-22 | Coordination of Benefits | Appeal guide → |
| CO-29 | Timely Filing Limit Expired | Appeal guide → |
| CO-45 | Charge Exceeds Fee Schedule | Appeal guide → |
| CO-50 | Not Medically Necessary | Appeal guide → |
| CO-96 | Non-Covered Charges | Appeal guide → |
| CO-97 | Bundled / Already Adjudicated | Appeal guide → |
| CO-119 | Benefit Maximum Reached | Appeal guide → |
| CO-167 | Diagnosis Not Covered | Appeal guide → |
| CO-197 | Precertification / Authorization Absent | Appeal guide → |
| OA-23 | Prior Authorization Required / Other Payer | Appeal guide → |
Frequently asked questions — Aetna appeals
- How long does Aetna have to respond to a Level-1 appeal?
- Aetna has 30 calendar days to respond to a Level-1 appeal. If the internal appeal is denied, you have 60 days from that denial to request external review by an Independent Review Organization (IRO). Your state's prompt-payment statute may impose a shorter window — verify before filing.
- How do I submit an appeal to Aetna?
- The fastest route is the Aetna provider portal. You can also fax appeals to 1-860-754-2985. Written appeals may be mailed to: Aetna Appeals Department, P.O. Box 14463, Lexington, KY 40512. Use certified mail with return receipt for any paper submission.
- What is Aetna's MHPAEA mental-health parity posture?
- 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.
- What are the most common Aetna denial codes for behavioral health?
- The most common Aetna denial codes for behavioral health practices are: CO-4, CO-97, CO-50, PR-96, CO-45. Select any code in the table above for the denial explanation, appeal strategy, and MHPAEA arguments.
- What should I include in a Aetna behavioral health appeal letter?
- A strong appeal should include: (1) the specific CARC or RARC denial code and reason for dispute; (2) clinical documentation supporting medical necessity; (3) a MHPAEA parity argument if the denial applies stricter criteria to mental health than to comparable medical services; (4) a written request for Aetna's NQTL comparative analysis under CAA 2021 § 203; and (5) your NPI, patient member ID, claim number, and date of service. AppealWin generates a complete, MHPAEA-grounded letter from your denial code in under 60 seconds.
Generate your Aetna appeal letter
AppealWin turns your denial code into a complete, MHPAEA-grounded appeal letter in under 60 seconds. First 5 letters free. No credit card required.
Generate my appeal letter →State-specific appeal rights
State prompt-payment windows and parity laws can strengthen your Aetna appeal. Select your state to see applicable statutes.
View all 50 states + DC →