Last updated: November 8, 2026. This post was corrected to use KFF’s plan-year 2024 figures, which were published in March 2026.
Quick answer: Among the large insurers KFF analyzed, Oscar Health had the highest in-network claim denial rate on HealthCare.gov in plan year 2024, at 25%. Elevance Health had the lowest, at 8%. The average across large insurers was 19%. These figures cover ACA marketplace plans only, not employer coverage, and most recorded denials are not medical necessity decisions.
Choosing a health plan by premium alone leaves out a question that matters when you need care: will the company pay the claim? Federal data shows the answer varies a lot by insurer. This article walks through what KFF’s analysis of the federal data found, what the numbers cover, and what to do if your own claim is denied.
What the Data Actually Measures
CMS requires insurers selling ACA marketplace plans on HealthCare.gov to report claims data every year. KFF analyzed the 2024 reporting in a brief published on March 24, 2026. It is a rare federally required, public look at how often marketplace insurers deny claims.
The figures cover claims for care that had already been delivered (post-service claims) in plan year 2024. They do not include requests for prior authorization made before care. Claims that were first denied and then resubmitted and paid are not counted as denials. Understanding this scope matters because an insurer’s full claims behavior includes categories this dataset does not capture.
Denial Rates for Large Insurers, Plan Year 2024
KFF reported that insurers on HealthCare.gov denied 19% of in-network claims in 2024 and 37% of out-of-network claims, for a combined average of 20%. Across individual insurers, in-network denial rates ranged from 3% to 36%. Among large parent companies (those with more than 5 million claims), rates ranged from 8% to 25%.
| Insurer (parent company) | In-network denial rate, 2024 | Notes |
|---|---|---|
| Oscar Health | 25% | Highest among large parent companies. Up from 17% in 2023. |
| Molina Healthcare | 22% | Second highest. Down from 26% in 2023. |
| Average across large parent companies | 19% | Similar to 2023. |
| Elevance Health | 8% | Lowest among large parent companies. |
Sources: KFF, Claims Denials and Appeals in ACA Marketplace Plans in 2024; Molina figures as reported by AP/NewsNation on the same KFF analysis.
KFF’s Table 1 lists every large parent company, including the other national carriers, with their 2024 rates. If you are comparing a specific insurer that is not in the table above, check that table rather than relying on older rankings. Figures from the 2023 reporting year are not interchangeable with 2024 figures, and some rankings still circulating online mix the two.
Reviewing rates like these matters just as much as comparing what you would pay out of your own pocket. Our guide to health insurance out-of-pocket costs covers the other side of that budget question.
Why a Single National Number Can Mislead
Averages hide wide differences. KFF found that state averages ranged from 27% in Hawaii to 7% in South Dakota. Individual Blue Cross Blue Shield companies, which operate independently of one another, are listed separately in KFF’s table for that reason. In the 2023 data, Blue Cross Blue Shield of Alabama had the highest rate among large parent companies, at 35%.
If your plan comes from a regional insurer or a Blue Cross Blue Shield company, what matters is the rate for your specific insurer in your state, not a national headline figure.
What Actually Causes Most Denials
A high denial rate sounds like insurers refusing care to sick patients. KFF’s data points to a more mixed picture. Among the denial reasons insurers reported for in-network claims in 2024:
- “Other” reasons not listed in the reporting categories: 36%
- Administrative reasons, such as duplicate, late or incomplete claims: 25%
- Excluded services: 13%
- Lack of prior authorization or referral: 9%
- Lack of medical necessity: 5%
KFF cautions that only limited reason data is available and that a claim can be denied for more than one reason, so these shares are indicators rather than an exact breakdown. Even so, most reported denials trace back to paperwork, coding and process issues rather than a decision that a recommended treatment was not needed.
That does not make denials harmless. A denied claim can still leave you with an unexpected bill and a confusing appeal process, whatever the underlying reason.
What This Data Does Not Tell You
- It covers non-group ACA plans sold on HealthCare.gov. It excludes employer-sponsored coverage and plans in states that run their own exchanges.
- Medicare Advantage plans are not included and are reported through a separate CMS process.
- Pre-service decisions, including denied prior authorization requests, are not part of this dataset.
- The figures reflect a single plan year and can shift as insurers change their processes and risk pools.
If your coverage comes through an employer rather than the marketplace, these percentages will not apply directly to your plan.
How to Check Your Own Plan Before You Enroll
You are not limited to national averages. The underlying CMS data is public. Look up your state and insurer in KFF’s tables or the CMS Transparency in Coverage public use files before open enrollment, which runs through January 15, 2027 on HealthCare.gov. Our guide to ACA open enrollment for 2027 has the current dates.
What to Do If Your Claim Is Denied
A denial is a starting point, not a final answer. Federal rules give you a path to challenge it.
- Read the denial letter to find the specific reason the insurer cited.
- Ask your doctor’s office to review and resubmit the claim if the issue looks like a coding or paperwork error.
- Ask the insurer for your claim file and the criteria it used to decide.
- File a formal internal appeal before the deadline in your denial letter. For ACA plans this is generally 180 days, but check your letter.
- If the internal appeal fails, request an external review through your state or the federal process.
KFF found that fewer than 1% of denied claims were appealed, and when consumers did appeal, insurers upheld their original denial 66% of the time. Because many denials are administrative, resubmitting or appealing is still worth trying. Families watching costs may also want to review how health insurance premiums are changing before choosing a plan for the coming year.
Frequently Asked Questions
Does a high denial rate mean an insurer is bad?
Not automatically. A high denial rate signals more friction in the claims process, but many denials stem from administrative and coding issues rather than a company refusing necessary care. Weigh denial rates alongside network access, customer service and your own healthcare needs.
Does this data include employer health plans?
No. The denial rates here come from non-group plans sold on HealthCare.gov. Employer-sponsored plans are not part of this analysis, so these percentages do not describe employer coverage.
What is the difference between an administrative denial and a medical necessity denial?
An administrative denial results from issues such as duplicate or incomplete claims, missing information or late filing. A medical necessity denial means the insurer decided the service did not meet its coverage criteria. In KFF’s 2024 data, medical necessity accounted for 5% of reported in-network denial reasons.
How often do appeals succeed?
Most internal appeals do not overturn the denial. KFF found insurers upheld 66% of internal appeals in 2024. Even so, fewer than 1% of denied claims were appealed at all, and administrative denials are often the easiest to fix through resubmission.
Which large insurer had the lowest denial rate?
Among large parent companies in KFF’s 2024 analysis, Elevance Health had the lowest in-network denial rate, at 8%. The highest was Oscar Health, at 25%.
Sources
- KFF: Claims Denials and Appeals in ACA Marketplace Plans in 2024 (March 24, 2026), based on CMS Transparency in Coverage public use files
- NewsNation: Health insurers rejected 19% of claims for exchange plans (Molina and Oscar figures reported from the KFF analysis)
This content is general insurance education only. Denial rates reflect ACA marketplace data for a single reporting year and may not represent your plan, state or employer coverage. Consult your insurer, your state insurance department or a licensed insurance professional for guidance on your situation.
