How to File a Health Insurance Appeal for a Denied Claim

A denial is a first decision, not a final one. The date printed on your notice starts every clock that matters from here, and which clock applies depends on what kind of plan you have.

A denied claim gets two levels of challenge: an internal appeal filed with your insurer, and then an independent external review of a health insurance denial by a reviewer your insurer does not control, whose decision it must follow. The clock on both starts from the date on your denial notice.

• Find the denial date on your notice — every deadline counts from it, not from the bill.
• Level one is the insurer reviewing itself; level two is an independent reviewer, and that decision is binding.
• Which deadlines apply depends on what kind of plan you have, so identify that first.
• If waiting could harm your health, both levels have an expedited track measured in days, not months.

Here is how to find the real reason for the denial, exactly what to send, and what happens if they say no a second time.

1. Start With the Letter: Find the Real Reason

A compliant denial notice — what regulators call an adverse benefit determination — has to state the specific reason for the denial, reference the plan provision it relies on, describe the appeal procedure and the applicable deadlines, and tell you about your external review rights. If any of that is missing or unclear, that is itself worth a phone call to your insurer before you write a word.

One of the least-used rights on this page is also one of the strongest: you’re generally entitled, free of charge and on request, to the documents and internal criteria your plan used to evaluate the claim — the clinical guideline, coverage policy, or rule the reviewer applied. Ask for it early. It often tells you exactly what your appeal needs to address.

An Explanation of Benefits (EOB) is not the same as a denial notice — an EOB is a running summary of what was billed and paid, while a formal adverse benefit determination is the document that triggers your appeal rights and deadlines. If you only have an EOB, call your plan and ask for the formal notice. For how your plan’s cost-sharing works day to day, see How Health Insurance Works: Deductible vs Out-of-Pocket Max — that’s a separate question from whether a claim was denied.

2. Why Claims Get Denied (and Which Ones Are Easy to Fix)

The most useful thing to know first: a large share of denials are administrative, not clinical, and many never need a formal appeal at all. A 2024 KFF analysis of HealthCare.gov marketplace data found that “other” and administrative reasons together accounted for the majority of stated in-network denial reasons, while lack of medical necessity accounted for only about 5%. Start by finding out which bucket yours is in.

Administrative and coding issues

A wrong billing code, a claim sent to the wrong plan, missing information, or a duplicate submission. These are often resolved with a phone call and a corrected resubmission from your provider’s billing office, rather than a formal appeal.

Prior authorization not obtained or denied

If care was never pre-approved, or the pre-approval request itself was denied, the appeal path differs slightly depending on whether the care has already happened — see the timing table in Section 4.

“Not medically necessary” or “experimental / investigational”

These turn on clinical judgment, not paperwork, and they’re the category most likely to end up at independent external review if your internal appeal doesn’t succeed.

Out-of-network and network issues

A denial can result from using an out-of-network provider or facility, or from a dispute about which network applied. This overlaps with how your plan’s network rules work generally — see HMO vs PPO: The Difference & Which Is Best for that background.

Plan exclusions and eligibility

Some denials are because a benefit isn’t offered under your plan at all, or because of a dispute about whether you were eligible or enrolled on the date of service. These require reading your plan document closely, not just the denial letter.

3. Which Appeal System Are You Actually In?

This is the fork the rest of the page depends on. The deadlines, the decision-maker, and whether independent external review is even available all change depending on which of these five categories your coverage falls into.

Marketplace or individual plan

Non-grandfathered individual and marketplace coverage generally follows the full ACA claims-and-appeals framework: an internal appeal with your insurer, then external review administered either by your state (if it runs a qualifying process) or through a federal process where it doesn’t.

Fully-insured employer plan

Most employer plans where the employer buys a policy from an insurance company also follow the ACA framework, with your state generally administering external review, because the underlying insurance policy is state-regulated.

Self-funded employer plan

This is the distinction most competing guides skip, and it changes your deadlines’ source and your external-review route. Many larger employers “self-fund” — the employer, not an insurance company, actually pays the claims, even though a familiar insurer’s name may be on your card as the administrator. Self-funded plans are governed primarily by the federal employee-benefits claims procedure regulation (29 CFR 2560.503-1) rather than state insurance law, because state insurance regulation generally does not reach self-funded ERISA plans. In practice the internal-appeal deadlines are the same as the ACA framework, but external review runs through a federal route: either a private accredited independent review organization supervised by the Department of Labor and the Treasury, or, for some plans, the HHS-administered federal external review process — not your state insurance department. Your summary plan description will say which.

Government program coverage

Medicare, Medicaid, and Medicare Advantage each run their own appeal systems, with their own names, levels, and deadlines — not the ACA process described on this page. Medicare Advantage, for example, uses a plan-level reconsideration followed by automatic referral to an independent entity under contract with Medicare if the plan upholds its denial. For the full walkthrough of that system, see Medicare Advantage Plans: Costs, Benefits & Picks.

Short-term or non-ACA arrangements

Certain short-term, non-ACA-compliant, or grandfathered coverage may not carry the same appeal and external-review rights described here at all. Check your notice and your plan documents directly, and don’t assume the rights on this page apply. If your coverage changed or lapsed around the time of the claim, Health Insurance Without a Job: Every Option and Real Cost covers what your options looked like and what changes between them.

Across all five categories, some things hold regardless of plan type, and some depend entirely on the plan you have:

• Guaranteed on every ACA-compliant plan: the right to an internal appeal, a written decision, and a copy of the criteria used on request.
• Guaranteed: an expedited track when waiting could seriously harm your health.
• Guaranteed: the right to name an authorized representative to file on your behalf.

• Varies by plan, state, or program: whether external review runs through your state or a federal process.
• Varies: the exact filing window — some plans and states allow more than the federal minimum.
• Varies: whether any external review right exists at all, for short-term and certain non-ACA coverage.

4. Level One: Filing the Internal Appeal

For ACA-governed plans — marketplace, individual, fully-insured employer, and, on the same timeline, most self-funded employer plans — you generally have at least 180 days (six months) from the date you receive the denial notice to file your internal appeal. Your plan or state may allow more time than that; the notice controls.

Once you file, the insurer’s decision timeframe depends on whether the care has already happened:

• Pre-service (care not yet received): a decision within 30 days.
• Post-service (care already provided): a decision within 60 days.
• Urgent care: a decision within about 72 hours.

You can file the appeal yourself, or name an authorized representative — a family member, friend, or your treating provider — to file and manage it on your behalf; a plan generally cannot block you from doing this. If your plan misses its own decision deadline, you’re generally treated as having exhausted your internal appeal rights already, meaning you can move on to external review — or, for many self-funded plans, directly to court — without waiting any further. For the federal rules behind both the ACA and ERISA timelines described above, see HealthCare.gov’s internal appeals guidance and the NAIC’s consumer guidance on appealing a denied claim.

5. The Appeal Letter: What Actually Goes In It

A useful appeal letter is direct, not long. Here is everything it needs:

• Identifying details — your name, member ID, and the claim and denial reference numbers.
• The date of the denial notice, so the reviewer can match your appeal to the right decision.
• A clear statement that you are appealing — say so in the first line.
• The specific reason the denial should be reversed, answering the exact reason printed on the notice, not the denial in general.
• A list of what you’re enclosing.
• A request for a written decision within the applicable regulated timeframe.

One line matters more than the rest: what you write and what your physician writes are two different things. You describe the timeline, the impact, and why you’re appealing. Your treating physician — not you — writes the clinical justification, called a letter of medical necessity, when one is needed. Your role is to request it from your doctor’s office and attach it; the letter never asks you to compose clinical content yourself.

• Your appeal letter — the cover statement, in your own words.
• A copy of the denial notice — so the reviewer has the exact decision you’re appealing.
• The plan’s criteria and documents you requested in Section 1, if you received them.
• The physician’s letter of medical necessity, if the denial turns on clinical judgment.
• Relevant medical records that support the claim.
• Plan language that supports coverage, if you found any.
• An authorized representative form, only if someone is filing on your behalf.

Send your appeal by a method that produces proof of delivery — certified mail, a tracked courier, or your plan’s confirmed portal upload — and keep a complete copy of everything you send, including the date.

6. Level Two: Independent External Review

An independent external review is administered either through your state’s process or through a federal process, depending on your plan type and state, as the fork in Section 3 lays out. Here’s the shape of it, regardless of which administers yours:

• Request window: generally 4 months after you receive the final internal denial notice.
• What you can submit: new information can generally be added at this stage, even if you didn’t include it in your internal appeal.
• Standard decision: generally within 45 days of the reviewer receiving your request.
• Expedited decision: generally within about 72 hours for urgent situations.
• Cost: where a fee applies, it’s capped at $25 per request, no more than $75 total in a plan year, refunded if you win, and waived if it would cause financial hardship. Many processes charge nothing.
• Binding effect: your insurer is required to accept the outcome if the independent reviewer sides with you.

These figures come from the ACA’s external-review regulation at 45 CFR 147.136 and HealthCare.gov’s external review guidance; self-funded employer plans use the parallel federal process described in Section 3 rather than a state one, with the same request window and decision timeframes.

7. Can AI Write Your Appeal Letter?

People are genuinely asking this, and most guides dodge it. Here’s a straight answer.

A language model can be genuinely useful for structure: organizing a messy timeline into clear paragraphs, keeping your tone measured, and turning your own notes into something a reviewer can follow quickly. That’s real, practical help, and there’s nothing wrong with using it that way.

What it must never be trusted with is the facts themselves. A language model can produce a confident, well-written sentence that cites a regulation, a plan provision, or a clinical detail that is simply wrong — fabricated citations and invented policy language are a documented failure mode of these tools, not a rare glitch. A single invented provision in your letter costs you credibility with the reviewer at exactly the moment you need it most.

Be careful about what you type into a third-party tool in the first place: medical details and identifying information don’t need to go into a general-purpose chat tool to get help with structure and tone. Consider removing names, member numbers, and specific clinical details when drafting, and add them back in only on the copy you actually send. And regardless of what a tool drafts, the clinical justification — the letter of medical necessity — must still be written by your treating physician. This article recommends no specific AI product for this purpose.

8. What Happens to the Bill While You Appeal

Filing an appeal does not, by itself, erase the balance on your account. Tell the provider’s billing office in writing that the claim is under appeal, and ask directly what will happen to your account status while it’s pending — some offices will hold or pause collections activity during an active appeal if you ask; none of them will do it automatically.

Hospital financial assistance and payment-plan options exist independently of your appeal and are worth asking about regardless of how the appeal turns out.

If a bill does reach collections, it follows its own separate credit-reporting rules — see Is Medical Debt Still on Your Credit Report? for that. Don’t ignore the bill while you wait; communicate about it in writing and keep a record of every call and letter.

9. How Often Appeals Actually Win

Two things are both true, and neither one is a personal prediction: appeals are rare, and a meaningful share of the ones people actually file succeed.

Among HealthCare.gov marketplace plans in 2024, insurers denied about 19% of in-network claims, and fewer than 1% of denied claims were ever appealed by the member — but when people did appeal, insurers reversed roughly a third of those decisions on internal review alone, before external review was even in play (KFF analysis of 2024 marketplace claims data).

Overturn rates vary a good deal by market segment. A separate KFF analysis of standard prior-authorization denials found that when people appealed, insurers reversed about 67% of denials in Medicare Advantage, 47% in Medicaid managed care, and 43% in the ACA Marketplace. These are averages across specific programs and years, not odds for any individual case.

What tends to distinguish a successful appeal, based on how the process is built: it addresses the stated reason on the notice directly rather than the denial in general, it supplies the specific documentation the plan’s own criteria call for, it meets its deadline, and — if level one doesn’t work — it goes on to level two instead of stopping.

10. When It Stops Being an Appeal

Two free routes exist alongside the appeal itself, not instead of it. A complaint to your state insurance department can flag a pattern or apply pressure, especially if your insurer is missing its own deadlines. Many states also run a consumer assistance program that helps people navigate an active appeal at no cost — Medicare.gov’s appeals guidance and your state regulator can point you to it.

For plans governed by the federal employee-benefits framework, exhausting the plan’s own appeal process is generally a required step before a lawsuit can be filed, and the record built during your appeal — what you submitted, when, and what the plan said back — is generally the record a court will actually look at. That’s the strongest argument for making the internal appeal thorough the first time, not an afterthought.

A lawyer becomes genuinely appropriate in a narrower set of situations: when the amount at stake is large, when the denial involves a rescission of coverage or a genuinely complex clinical dispute, or when the plan has repeatedly ignored its own deadlines. This isn’t a referral list — talk to your state bar’s referral service or a consumer-law clinic if you get to this point.

11. Frequently Asked Questions

What should I do first when a claim is denied?

Find the denial date on the notice — every deadline is measured from it. Then identify what kind of plan you have, since that decides which rules and which deadlines apply to you.

How long do I have to appeal a denied health insurance claim?

For ACA-governed plans — marketplace, individual, fully-insured employer, and most self-funded employer plans — you generally have at least 180 days from the date you receive the denial notice. Government programs like Medicare Advantage use their own, shorter windows. Your own notice always controls.

What is the difference between an internal appeal and an external review?

An internal appeal is your insurer reviewing its own decision. An independent external review of a health insurance denial hands the decision to a reviewer your insurer does not control, and that decision is binding.

Is an external review decision binding on my insurer?

Yes. When the independent reviewer sides with you, your plan is required to cover the claim.

Can I appeal if my plan is through my employer?

Yes. Fully-insured employer plans generally follow the same ACA rules as marketplace plans. Self-funded employer plans follow a federal claims regulation with the same general filing window, but a different, federal external-review route rather than your state’s process.

How long does the insurer have to decide?

Generally 30 days for a service you haven’t received yet, 60 days for a service already provided, and about 72 hours if the appeal is urgent.

What is an expedited appeal and when can I ask for one?

An expedited, or urgent, appeal applies when waiting for a standard decision could seriously jeopardize your health. It’s decided in about 72 hours, and in genuinely urgent situations you can sometimes request external review at the same time as your internal appeal.

Can my doctor file the appeal for me?

Yes. You can name your physician, or another person, as your authorized representative to file and manage the appeal on your behalf.

What should a health insurance appeal letter include?

Your identifying details, the claim and denial reference numbers, the date of the notice, a clear statement that you’re appealing, the specific reason the denial should be reversed, a list of what you’re enclosing, and a request for a written decision.

What is a letter of medical necessity and who writes it?

It’s a clinical statement, written by your treating physician, explaining why the denied care was needed. It is never something the patient writes.

Can I use AI to write my appeal letter?

It can help organize and clarify your own account, but it should never be trusted to supply facts, citations, or clinical claims — every factual line needs to be verified against your own denial notice and plan documents before you send anything.

Does external review cost anything?

Where a fee applies, it’s capped at $25 per request and $75 a year, refunded if you win, and waived for financial hardship. Many processes don’t charge at all.

Can I appeal a prior authorization denial before I get the care?

Yes — that’s treated as a pre-service appeal, generally decided within 30 days, or about 72 hours if it’s urgent.

Do I have to pay the bill while my appeal is pending?

Filing an appeal doesn’t erase the balance on its own. Tell the provider’s billing office in writing that the claim is under appeal and ask what your account status will be in the meantime.

What happens if the insurer misses its own deadline?

You’re generally treated as having exhausted your internal appeal rights already, which means you can move on to external review — or, for many plans, directly to court — without waiting further.

What are my options if I lose the external review?

For many plans, that decision is generally the end of the administrative process. For plans governed by the federal employee-benefits framework, having exhausted the appeal process may also open the option of pursuing the matter in court. A state insurance complaint or consumer assistance program can still help with related issues even after external review.

This article is for educational and informational purposes only and is not legal, medical, or insurance advice. Appeal rights, filing deadlines, decision timeframes, and external review procedures are set by federal law and regulation, vary by plan type and by state, may be more generous than the federal minimum, and can change. The deadlines and instructions printed on your own denial notice and in your plan documents govern your claim. The tools on this page organize general information and your own entries; they do not evaluate your claim, do not provide medical justification, and do not guarantee any outcome. Statistics cited reflect published analyses of specific market segments in specific years and are not a prediction about any individual appeal. The provisions described here were verified against federal regulations and official consumer guidance as of publication. Contact your plan, your state insurance department, or a qualified professional about your own situation.

Last updated: August 25, 2026