About one in five health insurance claims filed through ACA marketplace plans gets denied, according to KFF research on 2024 marketplace data. Despite that, fewer than 1% of patients appeal. That gap matters: 34% of internal appeals succeed in overturning the original denial. If your insurer said no, that denial is not necessarily the final word.
This guide walks through every step of the 2026 appeals process, from reading your denial letter through requesting an independent external review.
Why Health Insurance Claims Get Denied
Understanding the denial reason is the first step to reversing it. Most denials fall into a handful of categories, and many are fixable with the right documentation.
Most common denial reasons in 2026:
- Not medically necessary: The insurer's clinical guidelines don't match your doctor's recommendation. A 2023 JAMA study found medical necessity denials increased 33% between 2020 and 2022. According to the American Medical Association, 94% of physicians say prior authorization requirements delay access to necessary care.
- Prior authorization missing or incomplete: The service required pre-approval that was not obtained before treatment.
- Out-of-network provider: You saw a provider not included in your plan's network.
- Coding or administrative errors: A wrong CPT code, mismatched member ID, or missing documentation triggers an automatic denial.
- Service not covered under your plan: The specific treatment or supply falls outside your plan's covered benefits.
- Duplicate claim: The same claim was submitted more than once.
- Eligibility issues: The insurer shows you were not enrolled on the date of service.
Administrative errors account for a large share of denials, which is why they can often be reversed without a formal appeal. Call your insurer first and ask whether the denial was due to a billing error. If it was, have your provider resubmit the corrected claim.
Step 1: Read the Denial Letter and Explanation of Benefits
Your insurer is required to send you a denial letter with a specific reason for the denial. Read it carefully. You should also request your Explanation of Benefits (EOB), which shows how the claim was processed.
Look for:
- The exact reason code and language used to deny the claim
- The specific benefits provision, guideline, or exclusion cited
- The internal appeal deadline (typically 30 to 180 days from the denial date)
- Contact information for your insurer's appeals department
- Information about your right to request the clinical criteria used in the decision
The CMS consumer fact sheet on appeals rights confirms that all ACA-compliant plans must provide this information in writing.
Step 2: Gather Your Documentation
Build a file before you write a single word of your appeal letter. The stronger your documentation, the higher your chance of reversal.
Documents to collect:
- Denial letter and EOB
- Original itemized bill from the provider
- Your insurance card and plan documents (Summary of Benefits and Coverage)
- Your doctor's notes, referral letters, or treatment plan supporting the service
- Any prior authorization approvals or correspondence
- Medical records showing diagnosis and treatment history
- Notes from every phone call with your insurer (date, time, name of representative, what was said)
If your denial was for "not medically necessary," the most important document is a letter from your treating physician explaining why the service was required. Ask your doctor's office to write a letter that directly addresses the insurer's specific clinical criteria, not just a general note.
Step 3: File an Internal Appeal
An internal appeal is a formal request for your insurer to reconsider the denial. Under the Affordable Care Act, every non-grandfathered health plan must offer an internal appeals process. Details are available at HealthCare.gov's internal appeals page.
Internal appeal deadlines in 2026:
| Claim Type | Deadline to File Appeal |
|---|
| Standard claims | 30 to 180 days from denial notice |
| Urgent/expedited care claims | At least 72 hours before the service date |
Internal appeal response timeframes your insurer must meet:
| Situation | Insurer Must Respond Within |
|---|
| Urgent care (expedited) | 72 hours |
| Non-urgent, service not yet received | 30 days |
| Non-urgent, service already received | 60 days |
How to file your internal appeal:
- Contact your insurer to request the internal appeal form and submission instructions.
- Write an appeal letter that references the specific denial reason and refutes it with evidence.
- Attach all supporting documentation, including your doctor's letter if applicable.
- Submit by certified mail or through your insurer's online portal, and keep a copy of everything.
- Note the date submitted and the case or reference number provided.
- Follow up in writing if you do not receive a response within the required timeframe.
Your appeal letter should be direct: state the claim number, the date of service, the denial reason, and why the denial is wrong. Attach specific medical records rather than summarizing them.
Step 4: Request an Expedited Appeal for Urgent Situations
If your health could be seriously harmed by waiting for a standard 30-day decision, you can request an expedited internal appeal. Your insurer must respond within 72 hours.
Expedited appeals apply when:
- You need a service urgently and cannot wait for a standard review
- You are currently receiving a course of treatment that may be interrupted
- Your doctor certifies that a delay would jeopardize your health
Request expedited status in writing, and ask your doctor to include a statement explaining the medical urgency.
Step 5: File an External Review If the Internal Appeal Fails
If your insurer upholds the denial after the internal appeal, you have the right to request an external review. An independent organization, not affiliated with your insurer, will review the case and make a binding decision.
Under the ACA, external review rights apply to all non-grandfathered health plans. CMS external appeals information outlines which types of denials qualify.
Key facts about external review in 2026:
- External review is free to you
- You must file within 60 days of receiving the final internal appeal denial
- Standard external reviews are decided within 45 days
- Expedited external reviews are decided within 72 hours
- The external reviewer's decision is legally binding on your insurer
- Consumers win about 45% of external reviews according to state-level data
How to request external review:
- File a written request with your insurer or directly through externalappeal.cms.gov
- Your insurer will send your case file to an accredited Independent Review Organization (IRO)
- You may submit additional documentation directly to the IRO
- The IRO will contact you with their decision and the reasoning
If your insurer is regulated by your state (which applies to most employer-sponsored plans), your state insurance department may run the external review process. Contact your state insurance commissioner's office for state-specific instructions.
Step 6: File a Complaint With Your State Insurance Commissioner
If you believe your insurer is acting in bad faith, handling claims improperly, or violating your appeal rights, file a complaint with your state insurance department. This can happen in parallel with your appeal process.
Your state insurance commissioner can:
- Investigate insurer conduct
- Order corrective action
- Provide information about your specific state rights that go beyond federal minimums
Find your state insurance department through the National Association of Insurance Commissioners at naic.org.
How to Appeal a Medicare Claim Denial
If your coverage is through Medicare, the appeal process is different from private insurance. Medicare has five levels of appeals.
Medicare claim appeal levels in 2026:
| Level | Who Reviews | Timeframe |
|---|
| 1. Redetermination | Medicare contractor | 60 days to request, 60 days to decide |
| 2. Reconsideration | Qualified Independent Contractor (QIC) | 60 days to request, 60 days to decide |
| 3. ALJ Hearing | Office of Medicare Hearings and Appeals | 60 days to request |
| 4. Medicare Appeals Council | Appeals Council | 60 days to request |
| 5. Federal District Court | Federal court | 60 days to request |
Medicare beneficiaries can also request an expedited appeal for Part C (Medicare Advantage) denials. Details are at Medicare.gov's appeals page.
Documents Needed for Any Insurance Appeal
No matter what type of plan you have, keep these documents ready before you file:
- Denial letter with reason code
- Explanation of Benefits (EOB)
- Original itemized medical bill
- Your Summary of Benefits and Coverage (SBC)
- Treating physician's letter of medical necessity
- Relevant medical records (diagnosis, treatment history, test results)
- Any prior authorization documentation
- Dated notes from all phone calls with your insurer
- Copies of all submitted claims and correspondence
Common Reasons Appeals Fail (and How to Avoid Them)
Knowing why appeals get rejected helps you avoid the same mistakes.
- Missing the deadline: Every appeal has a hard deadline. Set a calendar reminder the day you receive a denial.
- Not addressing the specific denial reason: A generic appeal letter rarely works. Respond to the exact language in the denial.
- Weak medical necessity documentation: A single sentence from your doctor is not enough. Request a detailed letter that addresses the insurer's clinical criteria by name.
- No supporting records: Assertions without documentation carry little weight. Attach records, not summaries.
- Submitting through the wrong channel: Confirm the correct address or portal for appeals, separate from regular claims submission.
When You Might Need Extra Help
For complex denials involving experimental treatments, rare diseases, or high-dollar claims, consider:
- Your state's Consumer Assistance Program (CAP): Many states offer free help navigating appeals. Find your state CAP at HealthCare.gov.
- A patient advocate: Organizations like the Patient Advocate Foundation offer free case management services.
- Your state insurance department: They can explain state-specific rights that may strengthen your case.
If you are dealing with a denial and also uncertain whether you are enrolled in the right plan, or whether better coverage options exist, checking your eligibility takes about two minutes. Check your eligibility now at CoveredUSA. It takes 2 minutes.
Frequently Asked Questions
How long do I have to appeal a denied health insurance claim?
You typically have 30 to 180 days from the date of the denial notice to file an internal appeal, depending on your plan. For Medicare, you generally have 60 days for each level of appeal. Check your denial letter for your specific deadline, and do not miss it, late appeals are almost always rejected.
How often do insurance companies reverse denied claims on appeal?
According to KFF's 2024 ACA marketplace data, 34% of internal appeals result in the denial being overturned. For external reviews, consumers win roughly 45% of cases. In Medicare Advantage, more than 80% of appealed prior authorization denials are overturned (KFF 2024). The success rate is high enough that appealing is almost always worth the effort.
Does appealing a health insurance claim cost me anything?
Filing an internal appeal costs nothing. External review is also free under federal law for ACA-compliant plans and Medicare. You only pay if you hire a private patient advocate or attorney, which is optional and generally not necessary for straightforward cases.
What is the difference between an internal appeal and an external review?
An internal appeal is reviewed by your insurance company. An external review is conducted by an independent organization not connected to your insurer. You must exhaust the internal appeal process first. External review decisions are legally binding on your insurer.
Can I get an expedited appeal if I need treatment urgently?
Yes. If a delay in the decision would seriously harm your health, you can request an expedited internal appeal with a 72-hour response window. Your doctor must certify the medical urgency in writing.
What if my insurer ignores my appeal or does not respond?
If your insurer fails to respond within the required timeframe, that is considered a denial by default and you can immediately proceed to external review. Document all submission dates and follow up in writing. File a complaint with your state insurance department if the insurer is non-responsive.
What types of denials can be sent to external review?
Under the ACA, you can request external review for any denial involving medical judgment, any determination that a service is experimental or investigational, and any rescission of coverage. Administrative denials based purely on billing errors are not eligible for external review but can often be corrected by resubmitting the claim.
Does appealing affect my relationship with my insurer or future coverage?
No. Filing an appeal is a federal right. Insurers cannot penalize you, cancel your coverage, or change your premiums because you filed an appeal. Document everything in case any retaliation occurs.
Sources: KFF, Claims Denials and Appeals in ACA Marketplace Plans 2024 | HealthCare.gov, How to Appeal | CMS, Appealing Health Plan Decisions | CMS, External Appeals | Medicare.gov, File an Appeal
