The data behind denied claims: denial rates by insurer, appeal success rates, total dollars denied, and why 99.8% of patients never fight back. All figures cited to primary sources.
Sources: CMS, KFF, AHIP, OIG, State Insurance Departments — Last updated February 2026
Fight Your Denial →These are the most-cited facts on US insurance denial rates. Each figure is linked to its primary source.
The Centers for Medicare & Medicaid Services found that Medicare Advantage plans denied 1 in 7 prior authorization requests in 2023 — many of which met coverage criteria and would have been approved under traditional Medicare.
Despite high success rates for appeals, fewer than 1 in 500 people with a denied claim file a formal appeal. The overwhelming majority of denials — 99.8% — go entirely unchallenged by patients who don't know their rights.
When policyholders do appeal with proper documentation and legal citations, they overturn the insurer's decision at rates between 57% and 80% depending on the denial type and appeal level. At external review, the overturn rate reaches 72%.
The average denied claim in the US is worth approximately $4,200 — making it financially significant for most patients. Yet most patients never challenge the denial, leaving billions on the table annually.
$262 billion in legitimate healthcare claims are denied by US insurers every year. This figure represents a massive transfer of cost from insurers back to patients — most of it never challenged.
US marketplace health plans deny approximately 17% of all in-network claims on average. Some insurers deny more than 30% of in-network claims. The variation between insurers is extreme.
Over 200 million individual insurance claims are denied each year in the United States alone. Combined with the 0.2% appeal rate, this represents an enormous unaddressed patient rights crisis.
Citing this data? Please attribute: "ClaimBack Insurance Denial Statistics 2026, compiled from CMS, KFF, and AHIP public data."
Based on CMS Medicare Advantage audit and enforcement data. These figures represent prior authorization denial rates for Medicare Advantage plan members. Rates vary by plan type and state.
Note: These are approximate figures from publicly available CMS audit reports and Congressional investigation data. Actual denial rates may vary by plan and year. Commercial (non-Medicare) plan denial data is less standardized.
Not all denials are equal — and neither are the odds of winning an appeal. Here is the breakdown by denial type, based on CMS external review data and peer-reviewed health policy research.
Prior auth denials — the most common Medicare Advantage denial type — are overturned approximately 70% of the time on appeal. CMS data shows these denials are frequently not clinically justified.
Medical necessity is the most common denial reason across all plan types. When appealed with proper clinical documentation and the treating physician's statement, approximately 60% are reversed.
Experimental treatment denials are harder to overturn but succeed roughly 45% of the time, particularly when supported by NCCN guidelines, peer-reviewed literature, or FDA breakthrough designations.
Out-of-network denials, especially for emergency care or when no in-network alternative was available, succeed on appeal approximately 55% of the time under federal balance billing and network adequacy rules.
Despite a 57–80% appeal success rate, fewer than 1 in 500 people with a denied claim ever challenge it. Understanding why reveals a system-wide patient rights failure.
Most patients don't know how to write a formal appeal letter that correctly cites ERISA, ACA Section 2719, CMS guidelines, and insurer-specific coverage determination guidelines (CDGs). The regulatory landscape is intentionally dense. An appeal that fails to cite the right statute often loses on procedural grounds alone.
A landmark JAMA study found that most patients are unaware they have a federally protected right to appeal under the Affordable Care Act (42 U.S.C. § 300gg-19) and ERISA. Insurers are not required to prominently explain this right in denial letters. Many denial notices bury appeal information in fine print.
Insurance appeals require patients to gather medical records, obtain physician statements, research regulatory grounds, and draft formal correspondence — often while seriously ill. The average successful appeal takes 8–12 hours of patient time. For people dealing with illness, this burden is effectively insurmountable without help.
Insurance companies project an image of finality in their denial letters. Language like "coverage not available under your plan" is designed to close the conversation. Most patients don't know that 57–80% of properly-filed appeals succeed — or that external review reverses insurer decisions 72% of the time.
Insurance denial and appeal data from key international markets. While the US has the most detailed public data, other countries show similar patterns of under-reporting and under-appealing.
The Financial Ombudsman Service (FOS) handles over 75,000 insurance complaints per year. Approximately 35% are upheld in the consumer's favour. FOS awards up to £375,000 per complaint.
The Australian Financial Complaints Authority (AFCA) received over 98,000 complaints in 2022/23 — a record high. Health insurance complaints via the Private Health Insurance Ombudsman (PHIO) rose 13%. AFCA awards up to AUD 1.08 million.
Singapore's Financial Industry Disputes Resolution Centre (FIDReC) handles insurance disputes up to SGD 100,000 free of charge. Cases are typically resolved within 6 months. MAS Notice 120 mandates insurer compliance.
UAE insurers must respond to all claims within 30 days under Central Bank of UAE (CBUAE) regulations. Dubai Health Authority (DHA) and Department of Health Abu Dhabi (DoH) also set strict claim processing standards for health insurance.
ClaimBack compiled these statistics from the following primary sources:
Where precise figures are not publicly available, approximate ranges are stated. Insurer-specific denial rate figures represent Medicare Advantage data and may differ from commercial plan rates. All data is subject to revision as primary sources update.
Last updated: February 2026. Next review scheduled: August 2026.
According to CMS 2023 data, 1 in 7 (approximately 14%) of Medicare Advantage prior authorization requests are denied. A 2022 OIG report found that 13% of prior authorization denials would have been covered under traditional Medicare, suggesting many denials are unjustified.
Only 0.2% of people with a denied insurance claim formally appeal, according to KFF analysis of CMS marketplace data. This means 99.8% of all denied claims go entirely unchallenged — despite 57-80% of properly-filed appeals succeeding.
The appeal success rate for denied insurance claims ranges from 57% to 80% depending on the denial type and appeal level. At external independent review (required by law under the ACA), policyholders succeed approximately 72% of the time. Prior authorization denials have the highest overturn rate at approximately 70%.
Among major Medicare Advantage insurers, UnitedHealthcare had the highest denial rate in CMS audit data at approximately 32% of prior authorization requests. Anthem BCBS followed at approximately 22%. Kaiser Permanente had the lowest at approximately 7%, attributed to its integrated care model.
Approximately $262 billion in healthcare claims are denied by US insurers annually, based on AHIP and CMS Transparency in Coverage data analysis. With over 200 million individual claims denied per year and an average denied claim value of approximately $4,200, the scale of unchallenged denials represents an enormous financial burden on patients.
Research identifies three primary barriers: (1) fear of complexity — patients don't know how to write an effective appeal; (2) unawareness of rights — most patients don't know they have a legally protected right to appeal under the ACA and ERISA; (3) time constraints — the process seems overwhelming when dealing with illness. Only 0.2% of denied claims are appealed despite 57-80% of appeals succeeding.
57–80% of properly-filed appeals succeed. ClaimBack generates a professional, regulation-citing appeal letter in 3 minutes — for free to analyze, $12 to send.
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Statistics sourced from publicly available data including CMS, KFF (Kaiser Family Foundation), AHIP, OIG HHS, AFCA, FOS, FIDReC, and other regulatory bodies. Insurer-specific figures are approximate and based on Medicare Advantage audit data — commercial plan rates may differ. Individual results may vary. ClaimBack is not a law firm and does not provide legal advice. Data last updated: February 2026.