Insurance Appeal Guides
Browse appeal guides by payer, denial code, state, or condition. Pick the guide that matches your claim, then generate your appeal letter.
Appeal guides by payer
Select a payer to see its published appeal channels, response windows, and denial-code guides. Appeal addresses and deadlines vary by plan and region and are best-effort references — always confirm the current address and filing deadline against your denial letter or Explanation of Benefits before you file.
Appeal guides by denial code
Select the CARC code from your Explanation of Benefits for a step-by-step appeal guide.
CO-4
Modifier Inconsistent with Procedure
CO-11
Diagnosis Inconsistent with Procedure
CO-15
Authorization Number Missing or Invalid
CO-16
Missing or Incomplete Information
CO-18
Duplicate Claim
CO-22
Coordination of Benefits
CO-29
Timely Filing Limit Expired
CO-45
Charge Exceeds Fee Schedule
CO-50
Not Medically Necessary
CO-96
Non-Covered Charges
CO-97
Bundled / Already Adjudicated
CO-119
Benefit Maximum Reached
CO-167
Diagnosis Not Covered
CO-197
Precertification / Authorization Absent
OA-23
Prior Payer Adjustment (Coordination of Benefits)
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