Data
Health Insurance Denial Statistics: What the Data Says
Health insurers deny tens of millions of claims every year. Most of those denials are never appealed. And when patients do appeal, they win a significant share of the time. The data makes one thing clear: the system is designed to make people give up — and it largely works.
Denial volume: how many claims are denied?
CMS data on ACA marketplace plans provides the most transparent public view of denial rates. Key findings from the most recent available CMS and KFF analysis:
- –Denial rates vary dramatically by insurer. KFF analysis of ACA marketplace plan data found denial rates ranging from under 2% to over 49% depending on the insurer, with a median around 17% of in-network claims denied.
- –In-network claims are denied at scale. Contrary to the assumption that most denials involve out-of-network care, a significant share of denials are for in-network services — meaning the patient followed the rules and was still denied.
- –Prior authorization is a major choke point. CMS data consistently shows prior authorization as one of the most common denial triggers, particularly for specialty drugs, procedures, and mental health services.
For employer-sponsored ERISA plans, systematic national data is more limited — the Employee Benefits Security Administration (EBSA) collects complaint data but does not publish aggregate denial rates. The employer plan market is larger than the marketplace; the denial volumes are presumed to be substantial.
Appeal rates: almost no one appeals
This is the most striking data point. Across ACA marketplace plans, fewer than 0.2% of denied claims are ever appealed internally, according to KFF analysis.
Read that again: of every 500 denied claims, roughly one results in an appeal.
The reasons are not mysterious. The appeal process is time-consuming. Documentation requirements are burdensome. Most people do not know that federal law gives them specific rights with specific deadlines, or what regulations apply to their plan type. The system creates friction at every step. Insurers benefit from that friction.
When patients do appeal, they win
KFF's analysis of ACA marketplace plan data found that insurers overturn approximately 40% of internal appeals they actually review. That is not a trivial share — it means that in 40% of cases where someone went to the effort of filing a formal appeal, the insurer reversed its own decision.
External review data is similarly encouraging. Under ACA plans, when consumers pursue independent external review, they prevail in a meaningful percentage of cases — and the external reviewer's decision is binding on the insurer.
The implication is significant: a large portion of the denials that are never appealed would have been overturned if someone had challenged them.
Why appeal rates are so low
Research on patient behavior and insurance systems consistently identifies the same barriers:
Complexity: Patients receive a denial letter, often written in opaque language, with no clear explanation of what specific federal rights they have or what their plan type means for the appeal process.
Document burden: An effective appeal requires gathering medical records, obtaining letters from physicians, and referencing specific plan documents. This is a multi-step process that many patients cannot easily complete.
Ignorance of rights: Most patients covered by ERISA plans have never heard of 29 CFR § 2560.503-1 or the "full and fair review" requirement. Most ACA plan members do not know they have a right to binding external review. The regulations exist; the awareness does not.
Deadline pressure: The 180-day appeal deadline sounds generous until you account for the time to gather records and draft a substantive letter. Many people either miss the deadline or run out of time to do it properly.
Perceived futility: The common belief — reinforced by anecdote and insurer behavior — is that appeals don't work. The data says otherwise.
What the data means for you
If you have received an insurance denial:
- –You are statistically far more likely to succeed on appeal than the appeal rate suggests most people believe.
- –Your insurer almost certainly processes enough denied claims to know that most go unchallenged.
- –The specific regulatory framework governing your plan — ERISA or ACA — gives you defined rights with enforceable deadlines. Those rights exist whether you use them or not.
The single most effective thing you can do is file an appeal that cites the specific federal regulations governing your plan. Rebuttal drafts that letter for $9.99.
Frequently asked questions
What percentage of insurance claims are denied?
KFF analysis of ACA marketplace plans found denial rates ranging from under 2% to over 49% by insurer, with a median around 17% of in-network claims. For employer-sponsored ERISA plans, systematic national data is limited, though EBSA receives thousands of benefit denial complaints annually.
Do insurance appeals succeed?
KFF data shows insurers overturn approximately 40% of internal ACA appeals they review. External review success rates are also substantial. However, fewer than 0.2% of denied claims are ever appealed — meaning most denials go uncontested despite the high rate of successful appeals.
Why do so few people appeal insurance denials?
Research identifies complexity, document burden, ignorance of federal rights, deadline pressure, and perceived futility as the primary barriers. The system creates friction at every step; fewer appeals means fewer overturned denials, which benefits insurers financially.
Data sources: KFF Health Insurance Marketplace Plan Denials analysis; CMS Transparency in Coverage data; EBSA Annual Report. All statistics cited are from publicly available federal and independent research.
See also: How to appeal a health insurance denial · ERISA appeal rights · Denial code directory
Not legal or medical advice. Rebuttal is a document drafting tool, not a law firm. Review your letter before submitting and consult a licensed professional for legal questions specific to your plan.