What percentage of health insurance claims are denied?

Per KFF's analysis of CMS transparency data, HealthCare.gov marketplace insurers denied 19% of in-network claims in 2024, with insurer-level rates ranging from 3% to 36%. Out-of-network claims were denied at 37%.

Which insurers deny the most claims?

Among parent companies processing over 5 million marketplace claims in 2024, KFF reports in-network denial rates ranged from 8% (Elevance Health) to 25% (Oscar Health). Rates vary widely by state and plan.

How many people appeal denied claims?

Fewer than 1% of denied in-network marketplace claims were appealed in 2024. Insurers upheld 66% of those internal appeals — and only a small fraction of upheld appeals went on to independent external review.

Health insurance denial rates: what the federal data shows

2024 PLAN-YEAR DATA · PUBLISHED BY CMS, ANALYZED BY KFF · UPDATED JULY 2026

Insurers selling on HealthCare.gov must report how many claims they deny. The most recent federal transparency data — for the 2024 plan year, analyzed by the nonpartisan health-policy group KFF — shows denials are common, wildly inconsistent between insurers, and almost never challenged.

19%

of in-network marketplace claims were denied in 2024

3–36%

denial-rate range across 157 reporting insurers

37%

of out-of-network claims were denied

<1%

of denied claims were ever appealed by consumers

The same claim, a different answer — depending on the insurer

Among parent companies that processed more than 5 million marketplace claims in 2024, KFF reports in-network denial rates ranging from 8% at Elevance Health (the lowest) to 25% at Oscar Health (the highest) — a three-fold difference for comparable populations. Geography compounds it: HealthCare.gov insurers averaged 27% denials in Hawaii versus 7% in South Dakota. KFF's interactive tables list each reporting insurer's rate.

Why claims were denied

Reasons insurers gave for in-network denials, 2024 (KFF analysis of CMS data)
Stated reason	Share of denials	What it usually means for you
“Other” (unspecified)	36%	The insurer didn't classify it — demand the specific reason; you're entitled to it.
Administrative	25%	Paperwork problems — often fixable by resubmission, not a judgment on your care. See denial codes.
Excluded service	13%	Verify the exclusion against your plan documents — miscategorization happens.
No prior authorization / referral	9%	Frequently reversible — see the prior-auth guide.
Not medically necessary	5%	The most beatable denial with a doctor's letter — see the guide.

The appeal gap

Fewer than 1 in 100 denied claims was appealed in 2024. Of those internal appeals, insurers upheld 66% — but that still means roughly a third of challenged denials changed at the first step, and only about 4% of upheld appeals were taken on to independent external review, where a physician outside the insurance company gets the final, binding word. The system's math is stark: denials are mass-produced, appeals are hand-made, and almost nobody makes one.

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Sources & method

KFF, “Claims Denials and Appeals in ACA Marketplace Plans in 2024” — analysis of the CMS Transparency in Coverage 2026 Public Use File (published September 26, 2025), covering HealthCare.gov insurers for the 2024 plan year.
Figures cover ACA marketplace (HealthCare.gov) plans only; employer, Medicare, and Medicaid coverage report differently. Insurer-level rates reflect parent companies with 5M+ claims.
Denial-reason categories are as reported by insurers to CMS; “denial” includes both full and partial denials of in-network claims.
This page summarizes published third-party analysis and links the primary source. It is general information, not legal or medical advice.