How to Appeal a Health Insurance Claim Denial: Step-by-Step

Your Right to Appeal

Under the Affordable Care Act (ACA), you have the legal right to appeal any health insurance claim denial. This applies to all individual and employer group health plans, including marketplace plans, employer coverage, and Medicare Advantage. Insurers are required to follow a standardized appeals process.

Step 1: Understand the Denial

When your claim is denied, you must receive:

• A written Explanation of Benefits (EOB) or denial notice
• The specific reason for denial
• Reference to the plan provisions, guidelines, or criteria used
• Instructions on how to appeal and the deadline
• Notice of your right to request the clinical criteria used to make the decision

Read the denial carefully. Common reasons include: "not medically necessary," "experimental/investigational," "out-of-network," "missing documentation," or "service not covered."

Step 2: Gather Documentation

Before filing your appeal, collect:

• Your Explanation of Benefits (EOB) showing the denial
• Medical records supporting the need for treatment
• Doctor's letter of medical necessity (ask your doctor)
• Peer-reviewed medical literature if the service is being denied as experimental
• Your plan's Summary of Benefits and Coverage (SBC) and Evidence of Coverage (EOC)
• Any previous authorization approvals for the same or similar services

Step 3: File an Internal Appeal

Your first step is always an internal appeal — directly with your insurance plan.

• Deadline: Usually 180 days from the denial notice (ACA requirement for marketplace plans)
• Timeline: Plans must respond within 30 days for pre-service denials, 60 days for post-service claims, 72 hours for urgent care
• Tip: Submit all documentation in writing, keep copies of everything, and note the date you submitted
• Expedited appeal: If your health is at risk, request an expedited review — plans must respond within 72 hours

Step 4: Request a Peer-to-Peer Review

Before or during your internal appeal, ask your doctor to request a peer-to-peer review. This lets your doctor speak directly with the plan's medical reviewer. Many denials are resolved at this stage — research suggests peer-to-peer reviews overturn 30–50% of initial denials.

Step 5: External Review (Independent Review Organization)

If your internal appeal is denied, you have the right to request an external review by an Independent Review Organization (IRO). The IRO is independent of your insurer, and its decision is legally binding on the insurer.

• Deadline: Usually 4 months after internal appeal denial
• Cost to you: Typically $0–$25 (some states require free external review)
• Timeline: IROs must decide within 45 days (standard) or 72 hours (expedited)
• For Medicare Advantage: Request a Qualified Independent Contractor (QIC) review, then an Administrative Law Judge hearing

Step 6: File a State Insurance Department Complaint

In parallel with your appeal, consider filing a complaint with your state insurance commissioner. This creates a formal record and may trigger a regulatory review of the insurer's practices. Find your state commissioner via our state directory.

Step 7: Seek Additional Help

• Patient advocate organizations — Many disease-specific nonprofits offer free appeals assistance
• State consumer assistance programs — ACA-funded programs help with appeals in many states
• Employer's HR department — If coverage is through work, HR may intervene on your behalf
• Attorney — For large claims, consult an ERISA or insurance attorney; many work on contingency

Appeals Success Rates

Don't be discouraged by an initial denial. According to CMS data:

• Internal appeals overturn 30–40% of denied claims
• External reviews overturn 40–60% of cases that reach that stage
• Medicare Advantage overturn rates often exceed 70% for PA denials

Persistence pays. Most denials that survive to external review were improperly denied.

Reviewed byPlaininsurer Editorial, Insurance Editorial Team · June 5, 2026

Appeals: How They Work and Who Wins

The CMS Transparency in Coverage public-use files include not only claim denial rates but also appeal-filing rates and appeal-overturn rates. Reading these three columns together turns a single denial-rate snapshot into a fuller picture of insurer behavior. An insurer can have a high denial rate but also a high overturn rate, which suggests aggressive initial adjudication that gets corrected on appeal. Alternatively, an insurer can have a moderate denial rate with a very low overturn rate, suggesting denials that are administratively harder to challenge.

What appeals data reveals

Appeals data fills three reporting gaps that denial rates alone cannot fill: it measures the regulatory feedback loop (how often plan determinations are reversed when contested), the consumer-friction load (how often policyholders find it worth their time to formally challenge a denial), and the operational responsiveness of the insurer (how quickly and rigorously appeals are handled). Where appeals overturn rates are very low across the entire market for a given line of business, the issue may be structural — plan design that excludes the disputed service — rather than carrier-specific.

Reading the appeals overturn distribution

Among the issuer-state rows in CMS Transparency in Coverage data, appeal overturn rates vary from under 5% to over 50%. A high overturn rate signals that a substantial portion of initial denials were not supported on review. Combined with a low appeals-filed rate, this can indicate that most policyholders do not pursue formal appeals even when they would likely succeed — a pattern with potential consumer-protection implications that the data reveals quantitatively.

The same data row that lets you see how often a plan denies claims also lets you see how often those denials are reversed on appeal — together, the two columns describe insurer behavior in much more depth than either alone.