Aetna Claim Denials Explained
Aetna Claim Denials Explained: Overview
Aetna has a 22% denial rate (KFF data), commonly due to missing prior authorization, late filing, coding errors, or medical necessity challenges. File within 90 days for in-network and 180 days for out-of-network. Understanding the CARC code is essential for effective appeals, which must be filed within 180 days of denial.
Key Requirements
- File Claims Timely: In-network: 90 days from DOS. Out-of-network: 180 days from DOS. Late claims are denied automatically and cannot be appealed.
- Verify Authorization: Check if the service requires prior authorization. Submit PA before service delivery; denied PAs can prevent claim processing.
- Confirm Medical Necessity: Ensure documentation supports coverage criteria. Include diagnosis codes, clinical notes, and physician orders with claims.
- Validate Coding: Verify CPT/HCPCS codes match the service rendered and the authorization (if applicable). Coding mismatches trigger denials.
- Check Patient Eligibility: Confirm coverage was active on the date of service. Coverage gaps or terminations result in eligibility denials.
Timeline & Process
Step 1: Receive Denial Notice . Aetna sends remittance advice (ERA) or Explanation of Benefits (EOB) with denial code (CARC) and reason.
Step 2: Identify the CARC Code . Reference the denial code to understand the specific issue (e.g., CO-16 = not authorized, CO-45 = charge exceeds maximum, CO-50 = frequency limit exceeded).
Step 3: Gather Supporting Documentation . Compile medical records, coding justification, clinical notes, and authorization records (if applicable).
Step 4: File Appeal Within 180 Days . Submit written appeal with clinical evidence. Aetna responds within 30 days (standard) or 60 days (second review if first denied).
Common Aetna Claim Denials
| CARC Code | Description | Prevention |
|---|---|---|
| CO-16 | Claim/service not authorized | Obtain prior authorization before service delivery |
| CO-45 | Charge exceeds maximum allowable | Verify fee schedule and allowed amount before billing |
| CO-50 | Frequency limit exceeded | Check frequency/duration limits in plan coverage rules before billing |
Appeal Process
File written appeal within 180 days with claim number, denial code, and clinical documentation addressing the denial reason. Submit via portal, fax, or mail. Aetna responds within 30 days. If denied, request second review (60-day response). If both internal reviews fail, request external review by independent organization.
Common Questions
What is Aetna's claim filing deadline?
In-network providers: 90 days from date of service. Out-of-network providers: 180 days from date of service. Late-filed claims are denied and cannot be appealed.
What is the most common Aetna claim denial?
CO-16 (not authorized), CO-45 (charge exceeds maximum allowable), and CO-50 (frequency limit exceeded) account for majority of Aetna denials. Many are preventable with prior authorization.
How long do I have to appeal an Aetna denial?
180 calendar days from the denial date. Submit appeal in writing with clinical documentation. Aetna must respond within 30 days. Second review, if denied, within 60 days.
Altair checks Aetna requirements before submission . flagging missing authorizations and coding mismatches in real time. See how Altair works.
This reference is for informational purposes. Payer policies change frequently. Always verify against Aetna's current provider documentation. Last updated: 2026-03-16.
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