How to Appeal a Medicare Coverage or Payment Denial

Short answer

Medicare and Medicare Advantage plans deny some claims every year. When that happens, you have the right to appeal. Original Medicare uses a five-level process: redetermination, reconsideration, an OMHA hearing, an Appeals Council review, and — if the amount is large enough — federal court. Medicare Advantage and Part D drug plans follow a similar five-level path with slightly different deadlines and names. Roughly half of first-level appeals succeed, though success rates vary by the type of denial and the documentation you provide. This guide walks through each step, with the 2026 deadlines, forms, and rules you need. According to KFF’s analysis of CMS Medicare Advantage data, approximately 80 percent of appealed Medicare Advantage denials are overturned in the beneficiary’s favor when the appeal reaches reconsideration — a signal that many initial denials would benefit from a formal appeal.

Are you appealing a denial, or filing a claim?

These are two different things, and readers often land on the wrong one.

• Filing a claim means submitting a bill to Medicare for services your provider hasn’t billed for you. Original Medicare providers almost always bill Medicare directly. You only need to file a claim yourself in rare cases — usually when you paid out of pocket for a covered service and want reimbursement. The form for that is CMS-1490S.
• Appealing a denial means asking Medicare or your plan to reverse a decision it already made. That’s what this guide covers.

If you’re looking for how to submit a claim to Medicare or how to fill out claim reimbursement forms, this is not the right article.

Before you appeal: four things to check first

Sometimes a denial is a paperwork problem, not a coverage problem. Before you file a formal appeal, check four things.

1. Look for a coding or billing error — and ask the office to resubmit. Many denials come from a billing code your doctor’s office got wrong. Call the office, ask them to review the code, and — if they find an error — request that they submit a corrected claim before you file a formal appeal. In practice, many coding and billing denials are resolved this way without any appeal at all. This is a common first step providers take once you flag the issue.

2. Confirm prior authorization was in place. If your plan required pre-approval and the office skipped it, ask them to file the request now and re-bill. Some plans still cover the service if the medical need is clear.

3. Check that the service was in-network. For Medicare Advantage, out-of-network care is a common denial reason. If you had a valid reason to go out of network — an emergency, or the plan sent you there — say so in your appeal.

4. Check the deadline on your notice. Your Medicare Summary Notice (MSN) or your plan’s Explanation of Benefits (EOB) shows the last day to appeal. If you miss it, you can still file with good cause — illness, a family death, a lost or delayed notice — but you have to explain why.

If none of these four fixes the problem, move to the formal appeal.

Request the full denial rationale before you draft your appeal

Before you start writing, ask the plan or Medicare contractor for a complete copy of the denial rationale — including any utilization management (UM) notes the plan reviewed. Denial notices sometimes list only a short code or generic reason (“not medically necessary,” “service not covered”) that hides the specific criteria the reviewer applied. When you have the full rationale, your appeal can respond directly to the reviewer’s own reasoning. Understanding the exact reason for the denial often strengthens an appeal materially.

For Original Medicare, request the redetermination file from the MAC listed on your MSN. For Medicare Advantage or Part D, call your plan’s member services line and ask for the full denial rationale plus any UM notes. Plans are generally required to share this information on request.

The 5 levels of a Medicare appeal (Original Medicare)

Original Medicare — Part A hospital and Part B outpatient care — uses a five-level appeals process. If you disagree with a decision at one level, you can move to the next.

Level 1 — Redetermination. Start with your MSN. Circle the item you disagree with, write a short explanation, attach any supporting notes from your doctor, and send it to the MAC address printed on the MSN. You can also use the CMS Redetermination Request Form (CMS-20027), though you are generally not required to use the official CMS form as long as your written request includes the beneficiary’s name, Medicare number, the specific service and date being appealed, the reason you disagree, and your signature. There is no single national mailing address for Medicare appeals — the correct address depends on your MAC, which is state-based, and is printed on your MSN itself. Send it by the deadline. The MAC will send a decision letter within about 60 days.

Level 2 — Reconsideration. If Level 1 says no, you have 180 days to ask for a Reconsideration from a Qualified Independent Contractor. Send it to the QIC named in your Level 1 decision letter. Include the QIC-assigned appeal number, dates of service, why you disagree, and any new medical records that support your case.

Level 3 — OMHA hearing. If Level 2 says no, you can ask an Administrative Law Judge at the Office of Medicare Hearings and Appeals to hold a hearing. To qualify, the amount in dispute must meet a minimum dollar amount set each year by CMS — check CMS.gov for the current-year figure. You can request a hearing by phone or video, or ask for a decision without a hearing.

Level 4 — Medicare Appeals Council review. If the ALJ says no, the Medicare Appeals Council can review the decision. This is a paper review, not a hearing. You have 60 days from the ALJ decision to file.

Level 5 — Federal District Court. The final level is a lawsuit in U.S. District Court. For 2026, the amount in dispute must be at least $1,960. You have 60 days from the Council’s decision to file.

If you have Medicare Advantage (Part C)

Medicare Advantage — plans run by private insurers like UnitedHealthcare, Humana, or Aetna — uses the same five-level structure with different names and shorter deadlines at Level 1.

The Level 1 appeal is called a “Reconsideration” and goes directly to your plan. You have 65 days from the date on the denial notice to file. The plan must decide within 30 days for a service you have not yet received, 60 days for a service you already got, and 72 hours if your health is at risk and you request an expedited review. Requirements for Medicare Advantage HMO referrals vary by plan — some plans require both a referral from your primary care physician and a prior authorization, others require only one, and a few require neither for certain specialists. Check your plan’s Evidence of Coverage before assuming a referral or prior authorization was needed.

If your plan denies your Level 1 appeal, they must automatically forward the case to Level 2 — the Independent Review Entity. As of May 1, 2026, the Part C IRE is C2C Innovative Solutions, Inc. (before that date it was MAXIMUS). If you filed an appeal on or before April 30, 2026, MAXIMUS is still processing it; new appeals go to C2C.

Levels 3 through 5 (OMHA hearing, Appeals Council review, federal court) work the same way as Original Medicare.

New for 2026: The CY 2026 Medicare Advantage final rule tightened plans’ ability to reverse previously approved inpatient admissions. Under the rule, a plan can only reopen an approved admission for obvious error or fraud. This gives you a stronger footing if a plan tries to walk back an approval after care has already been delivered.

If you have a Medicare drug plan (Part D)

Part D coverage starts with a coverage determination — a decision by your drug plan about whether it will pay for a specific medication. If your plan says no, you can ask for a redetermination.

The Part D appeal path:

• Level 1 — Redetermination. Filed with your plan. You have 65 days from the initial denial. Standard decision within 7 days; expedited within 72 hours.
• Level 2 — Reconsideration. Filed with the Part D Independent Review Entity. You have 60 days from the Level 1 denial.
• Levels 3 through 5. OMHA hearing, Appeals Council, federal court — same structure as Original Medicare and Medicare Advantage.

If your plan does not cover a specific drug, you can ask for a formulary exception — a decision by your plan to cover a drug outside its normal list, when your prescriber writes a statement of medical necessity. Formulary exception requests are often denied because the prescriber’s supporting statement doesn’t include enough clinical detail — a bare “medically necessary” note without the diagnosis, prior therapies tried, and specific clinical reasoning that rules out formulary alternatives. If your first exception request was denied on those grounds, ask your prescriber to submit a more detailed clinical statement with the appeal.

Fast appeals when Medicare says your care is ending — act immediately

If you’re in a hospital, skilled nursing facility, home health agency, hospice, or comprehensive outpatient rehabilitation facility and Medicare says your covered stay is ending, you have the right to a fast appeal. This is a separate track from the standard five-level process, and the window is extremely short: you generally must request the review by noon the day after you receive the Notice of Medicare Non-Coverage. Call as soon as you receive the notice, not after you’ve thought about it. If you file on time, your covered care continues while the review is under way.

• Ask for a review by the Beneficiary and Family Centered Care Quality Improvement Organization (BFCC-QIO). In 2026 the two BFCC-QIO contractors are Acentra Health (formerly KEPRO) and Commence Health (formerly Livanta) — the one that handles your case depends on your state. The CMS BFCC-QIO landing page has a lookup map. (If you see older articles that still reference “KEPRO” or “Livanta” as the contractor to call, they’re using the pre-2024 names for the same organizations.)
• You must request the review by noon the day after you get the written notice that your care is ending — sometimes called the “Notice of Medicare Non-Coverage.”
• The BFCC-QIO decides within about 72 hours. Your covered care continues while the review is under way if you file on time.

Important 2026 update: The retrospective appeals window for patient-status reclassifications under the Alexander v. Azar rule closed on January 2, 2026. If a hospital reclassified you from inpatient to outpatient observation after that date, you can no longer file a retrospective appeal without showing good cause for late filing. The prospective fast-appeal path — asking for review while you are still admitted — is unaffected.

When this guide doesn’t cover your appeal

Three types of Medicare-adjacent appeals fall outside the process above.

• IRMAA appeals — If Social Security raised your Part B or Part D premium because of your income (the Income-Related Monthly Adjustment Amount), you appeal to Social Security, not Medicare. File form SSA-44 if a life-changing event lowered your income. See ssa.gov/medicare/lower-irmaa.
• Late enrollment penalty (LEP) appeals — Part B or Part D late-enrollment penalties are appealed through a separate reconsideration process. For Part D, you have 60 days from the notice; ask your plan for a reconsideration request form.
• Medicaid appeals — Medicaid uses a separate appeals process run by each state Medicaid agency. If you have both Medicare and Medicaid (dual eligibility), your appeal goes to whichever program made the disputed decision.

The forms you’ll need

Most Medicare appeals accept a plain letter, but named CMS forms make the process cleaner:

• CMS-20027 — Medicare Redetermination Request Form. Used at Level 1 for Original Medicare. Download from CMS.gov.
• CMS-1696 — Appointment of Representative. Fill this in when you want a family member, friend, attorney, or advocate to file the appeal for you.
• OMHA-104 — Request for ALJ Hearing. Used at Level 3 (OMHA) for Original Medicare and Part D.
• Plan-specific reconsideration forms. Medicare Advantage plans and Part D plans have their own Level 1 appeal forms. Find them in your plan materials or on the plan’s website.

CMS-1500 is not an appeals form. The CMS-1500 is used to file an original claim for services. If you find a reference to it while researching your appeal, it’s the wrong form. Appeals use CMS-20027 and the plan-specific reconsideration forms above.

Print two copies of everything you send. Keep one. Send the other with proof of delivery — certified mail or fax with confirmation.

Keep a communication log and a medical-events timeline

Two habits make an appeal materially easier to run — especially if it moves through multiple levels.

Communication log. Keep a running log with the date and time of every call, the name and reference number of the representative you spoke with, and a two-sentence summary of what was said. If you send a letter or fax, note the delivery method and the confirmation number. If you email, save the message. Later levels of appeal often turn on being able to show what you were told and when — and a communication log is that record.

Medical-events timeline. Build a one-page timeline of key medical events: diagnosis dates, treatments, tests, medication changes, hospital admissions, and any denial dates. Reviewers evaluating an appeal have to reconstruct your care history from scattered records; a clean timeline makes the medical necessity of the disputed service easier to see at a glance.

Keep copies of everything — the original denial notice, your appeal letter, supporting documents, fax confirmations, certified mail receipts, and every decision letter that comes back. Store paper copies in a folder and digital copies in one place. If your appeal escalates to Level 2 or beyond, you’ll need to include the earlier decisions and your responses to them.

What to include in your appeal letter — and how to win

A good appeal letter is short, specific, and grounded in medical fact. Include these six things:

1. Your name, address, phone number, and Medicare number. Your Medicare number appears on your red-white-and-blue Medicare card and on every Medicare Summary Notice. Include it on every document you send.
2. The claim number and dates of service you are appealing.
3. The exact denial reason (copy the wording from your MSN or EOB).
4. What outcome you are asking for — coverage, payment, a change to the billing amount.
5. Why you believe the decision was wrong. Reference specific medical facts.
6. Supporting documents: your doctor’s notes, medical records, prescription history, test results.

Sample opening paragraph:

To Whom It May Concern, I am appealing Medicare’s denial dated [date] for [service or item] provided on [date of service]. My claim number is [claim number]. Medicare denied coverage on the grounds of [reason from your notice]. I disagree with this decision because [medical explanation], and I am asking Medicare to reconsider and cover this service. I have attached my doctor’s supporting statement and relevant medical records.

To win the appeal, name the exact denial reason in your first sentence, cite the specific dates of service, and attach a physician’s letter that explains — in clinical detail — why the service meets Medicare’s coverage criteria for your specific diagnosis. A generic letter saying “this service is medically necessary” is less persuasive than one that names the diagnosis, cites the relevant Medicare coverage rule (Local Coverage Determination or National Coverage Determination if applicable), lists prior therapies tried and their outcomes, and explains why alternatives are not appropriate for your case. According to studies published by the HHS Office of Inspector General and KFF, appeals supported by detailed physician documentation succeed at higher rates than those with generic medical-necessity statements — though outcomes still vary by the type of service and the specific denial reason.

Skilled nursing facility appeals — how to win. SNF denials often turn on whether the facility documented ongoing skilled need day by day. If your appeal is about a skilled nursing stay, ask the facility for a copy of the physician’s certification of continued need and every day’s therapy or nursing notes. The certification is the single most important document. Without it, an SNF appeal rarely reverses; with it, plus the day-by-day notes, the odds shift in your favor.

What’s new for 2026

Four 2026 updates change how appeals work compared to earlier guides you might find online:

• Retrospective patient-status appeals closed (Jan 2, 2026). The 365-day retrospective window under the Alexander v. Azar final rule ended. Post-Jan 2, 2026, retrospective requests need good-cause justification.
• Part C IRE change (May 1, 2026). Level 2 appeals for Medicare Advantage now go to C2C Innovative Solutions, Inc. — not MAXIMUS. Any 2025-era contact information for MAXIMUS is out of date for new appeals.
• MA plans held to approved admission decisions. The CY 2026 Medicare Advantage final rule restricts when a plan can reopen an approved inpatient admission. This helps beneficiaries and providers who have already been told an admission is covered.
• 2026 judicial review threshold: $1,960. Up from $1,840 in 2024. This is the minimum amount in dispute for a Level 5 federal court appeal.

When a patient advocate helps — and when they don’t

An appeal is paperwork, evidence, and deadlines. It can also be emotionally exhausting when you’re already dealing with a health issue. A patient advocate — someone who understands the appeals system and takes on the calls, the drafting, and the follow-up — often makes the difference between an appeal that stalls and one that gets a fair review.

Baba’s advocates work with clients on Medicare denials every day. Their role goes beyond drafting the appeal letter: an advocate typically coordinates your medical records across providers, communicates directly with the insurance plan and treating physician to close documentation gaps, monitors every deadline across appeal levels, and ensures supporting documents — physician letters, test results, prior-authorization history — are complete before the appeal is filed. They also flag when a peer-to-peer review or a formulary exception is a better path than a full appeal. Most of Baba’s advocacy work is covered by Medicare, so most clients pay nothing out of pocket. If a specific piece of work is not covered, Baba tells you before doing it — no surprise bills. For more on what an advocate does, when to call one, and what’s free, see Baba’s service overview.

When an advocate is not the right answer:

• If the denial is a simple coding error, your doctor’s billing office can fix it in one phone call. No advocate needed.
• If you want free, in-person counseling on Medicare in general, your State Health Insurance Assistance Program (SHIP) offers this at no cost. Find your state’s SHIP at shiphelp.org.
• If your appeal has reached the federal-court level (Level 5), you’ll likely need an attorney, not just an advocate.
• If your problem is a quality-of-care concern rather than a coverage denial — a rude nurse, a delayed test — you file a grievance with your plan, not an appeal. These are different processes.