Health claim denials are common, and few people challenge them. A KFF analysis published in January 2025 found that insurers selling plans on HealthCare.gov denied about 19% of in-network claims and 37% of out-of-network claims in 2023. Consumers appealed only about 1% of denied in-network claims, and insurers upheld their original decision in 56% of those appeals. In other words, a large share of the appeals that were filed succeeded. Knowing the process and its deadlines improves your odds.
Why health claims get denied
- Administrative errors: wrong billing code, missing information, duplicate claim, provider not credentialed.
- No prior authorization or referral where the plan requires one.
- Not medically necessary in the insurer's view, or considered experimental.
- Excluded service or out-of-network care not covered by your plan type.
- Eligibility: coverage lapsed or the person was not enrolled on the date of service.
Start by reading the Explanation of Benefits (EOB) and the denial notice. Billing errors are often fixed with a phone call to the provider's billing office, without a formal appeal.
Your rights under the Affordable Care Act
For most private health plans, the Affordable Care Act gives you two levels of review: an internal appeal to the insurer and, if that fails, an external review by an independent reviewer. The deadlines below are those published on HealthCare.gov.
| Step | Deadline |
|---|---|
| File an internal appeal | Within 180 days (6 months) of the denial notice |
| Insurer decides: service not yet received | Within 30 days |
| Insurer decides: service already received | Within 60 days |
| Urgent care appeal | As fast as your condition requires, and no later than 4 business days |
| Request external review | Within 4 months of the final internal denial |
| External review decision | Within 45 days; expedited within 72 hours |
How to write a strong internal appeal
- Use the insurer's form or a letter that includes your name, member ID, claim number and the service denied.
- Quote the reason given in the denial and answer it directly.
- Attach a letter of medical necessity from your doctor explaining why the treatment is needed, why alternatives are not suitable and which clinical guidelines support it.
- Add records: test results, notes on treatments already tried, and published studies if the denial says the care is experimental.
- Ask for the plan documents and the clinical criteria the insurer used. You are entitled to see the information relevant to your claim.
- Keep copies and send by a method that proves delivery. Note every call.
If your situation is urgent, ask for an expedited appeal. HealthCare.gov notes that in urgent cases you can request an external review at the same time as the internal appeal.
External review
If the insurer upholds its denial, the written decision must explain how to request an external review. Depending on your state and plan, the review is run by your state, by the federal government (HHS) or by an independent review organization. According to HealthCare.gov, the federal process is free, and a state or contracted process may charge no more than $25. The reviewer either upholds the denial or decides in your favor, and the insurer is required by law to accept the external reviewer's decision.
Plans with different rules
- Employer plans: most job-based plans follow similar appeal rules, but self-funded employer plans are governed by federal law (ERISA) rather than state insurance law. Your summary plan description explains the process.
- Medicare and Medicaid have their own appeal systems with separate levels and deadlines.
- Grandfathered plans that existed before the ACA and short-term plans may not have to follow all ACA appeal rules.
Where to get help
- Your state insurance department can explain the external review process and accepts complaints about insurers.
- Many states have consumer assistance programs that help with appeals at no cost.
- Your doctor's office often has staff who handle prior authorizations and appeals every day.
Practical tips
- Do not ignore bills while the appeal is pending; ask the provider to put the account on hold.
- For planned care, ask for prior authorization in writing before the procedure.
- Check whether the denial relates to network status. Out-of-network denials were nearly twice as frequent as in-network denials in the KFF data.
For general questions about marketplace coverage, see our health insurance section and the upcoming guide to Affordable Care Act basics. Rules and deadlines can change, so always confirm them on your denial notice and with your plan.