How do I appeal a denied claim?

The appeal process has predictable steps. First, identify the denial reason from the CARC (Claim Adjustment Reason Code) and RARC (Remittance Advice Remark Code) on the EOB or 835 remittance. X12's code committee maintains the CARC list and CMS maintains the RARC list, and together they tell you what the payer says went wrong. Second, gather supporting documentation: clinical notes proving medical necessity, prior authorization confirmation, eligibility verification at date of service, corrected claims with proper modifiers, and any contractual documentation. Third, submit the appeal within the payer's deadline. Medicare gives you 120 days from receipt of the initial determination to request a redetermination, then 180 days from receipt of that decision to request reconsideration by a Qualified Independent Contractor. For ACA-compliant plans the patient has 180 days from the denial notice to file an internal appeal, and your provider contract may set its own window for your appeals. The appeal letter should reference the specific CARC, explain why the denial was incorrect, and attach supporting documentation. Fourth, if denied at first level, escalate to second-level appeal, then to external review (state-mandated for fully insured plans, ERISA for self-funded). Under the federal standards the external review request is due within 4 months of the final denial, and a standard review must be decided within 45 days. Fifth, track every appeal in a log and measure your overturn rate. Commercial overturn rates are rarely published, but KFF's analysis of Medicare Advantage data shows that 80.7 percent of appealed prior authorization denials were fully or partly overturned in 2024, while only 11.5 percent of denials were appealed at all. The bottleneck is timely filing; missed appeal deadlines convert recoverable revenue to permanent loss.