How do I understand what an eob is (and is not)?

An Explanation of Benefits is not a bill. It is a summary showing what Medicare received from your provider, what Medicare paid, and what you may owe. Your provider will send you a separate bill if payment is needed.

How do I find your eob — paper or online?

Paper Medicare Summary Notices arrive every three months by mail. Electronic notices (eNotices) are available sooner at medicare.gov → My Account → Claims & Appeals. You can sign up for electronic notices to get them faster.

How do I read the four key dollar amounts?

Billed amount: what your provider charged. Medicare-approved amount: what Medicare agreed to pay. Medicare paid: the actual payment to your provider (usually 80% of approved). You may be billed: your share (usually 20% of approved, plus any deductible).

How do I check each claim for errors?

Compare every claim to your own appointment records. Look for dates you did not visit a doctor, providers you do not recognize, procedures that do not match what happened, or duplicate charges for the same visit.

How do I report errors or fraud?

Call 1-800-MEDICARE (1-800-633-4227) any time, 24/7, to ask about a claim. For suspected fraud, also report to the HHS Office of Inspector General at 1-800-447-8477 or oig.hhs.gov.

How do I understand your medigap supplement plan?

If you have a Medigap (Medicare Supplement) plan, your insurer automatically receives the claim from Medicare after Medicare pays its 80%. Your Medigap plan pays your 20% share directly to the provider. You usually owe $0 for covered services.

How to Read Your Medicare Explanation of Benefits Letter — Step-by-Step Guide

Every few months, you may receive a thick envelope from Medicare with the words "Medicare Summary Notice" printed on it, or you may see a notice in your Medicare account online. Many people set these letters aside unread because the numbers and terms look confusing. However, reading your Explanation of Benefits (EOB) carefully is one of the best ways to catch billing errors and protect yourself from Medicare fraud.

This guide explains what every section of the EOB means, what to look for, how to report errors, and what to do if you have a Medicare supplement plan.

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What is an Explanation of Benefits?

First, the most important thing to know: **an Explanation of Benefits is not a bill.** It is an informational summary. It tells you that Medicare received a claim from one of your healthcare providers, what Medicare paid, and what — if anything — you may owe. You should never send money to anyone based only on an EOB.

If you do owe money (for example, a copay or the 20% coinsurance you are responsible for under Original Medicare), your provider — the doctor's office or hospital — will send you a separate bill. The EOB is a record of what happened with the claim.

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Two formats: paper and online

Medicare Summary Notice (MSN):

The paper version mailed to your home. Medicare mails this every three months if you are in Original Medicare (Part A and Part B). It covers all claims from that quarter.

eNotice:

The electronic version. If you have a Medicare.gov account and have signed up for electronic notices, you will receive an email when your eNotice is ready and can view it at medicare.gov → "My Account" → "Claims & Appeals." The online version is available sooner than the paper version.

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The four key dollar amounts explained

Every claim listed on your EOB will show four numbers. Here is what each one means:

1. Billed amount (or Amount charged)

This is what your provider — the doctor, hospital, or lab — originally charged Medicare. This number is often much higher than what Medicare actually pays. Providers agree to accept Medicare's approved rate, so the billed amount is not what you actually owe.

2. Medicare-approved amount

This is the amount Medicare has agreed is a reasonable payment for this service. Both Medicare and you base your shares on this number — not the billed amount.

3. Medicare paid

This is what Medicare actually sent to your provider. Under Original Medicare Part B, Medicare usually pays 80% of the Medicare-approved amount (after your deductible has been met).

4. You may be billed

This is your share — usually the remaining 20% of the Medicare-approved amount. You may also see your Part A or Part B deductible listed here if it applies to this claim. This is the amount your provider is allowed to charge you.

Example in plain numbers:

A doctor charges $350 (billed amount). Medicare's approved amount for that visit is $200. Medicare pays 80% of $200 = $160. Your share is 20% of $200 = $40. The doctor cannot charge you the difference between $350 and $200 — that $150 "write-off" is absorbed by the doctor as part of their Medicare agreement.

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What to look for: catching errors and fraud

Not every mistake on your EOB is fraud — billing errors are common. And they can cost you or Medicare money. When you receive your EOB, check each claim against your own records (appointment calendar, medical paperwork). Look for:

**A date of service you do not recognize.** If Medicare shows a claim for a visit that did not happen, this is either a billing error or potential fraud.
**A provider you have not seen.** If you see a doctor's name or a lab you do not recognize, call Medicare to ask about it.
**A procedure that does not match what was done.** Each claim includes a description of the service (for example, "Office visit, 15 minutes" or "Blood test, basic metabolic panel"). If the description does not match what happened at your appointment, the provider may have billed for the wrong service.
**Duplicate charges.** Two claims for the same visit on the same date may be an error.

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How to report a billing error or suspected fraud

By phone:

Call 1-800-MEDICARE (1-800-633-4227). Representatives are available 24 hours a day, 7 days a week. Tell them you have a question about a claim on your Medicare Summary Notice and give them the date of service and the provider name.

Online:

Go to medicare.gov, sign in, and navigate to "Claims & Appeals." You can view your claims and submit a question about any claim.

For suspected fraud:

Medicare has a dedicated fraud reporting line. You can also report fraud to the HHS Office of Inspector General at 1-800-HHS-TIPS (1-800-447-8477) or online at oig.hhs.gov. Reporting Medicare fraud is anonymous if you prefer. And it helps protect other Medicare recipients.

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If you have a Medicare Supplement (Medigap) plan

A Medigap plan is extra insurance you buy from a private company to cover the costs that Original Medicare does not pay — your 20% coinsurance and deductibles. If you have Medigap, here is how it works:

When your doctor submits a claim to Medicare, Medicare processes it first and pays its 80%. Medicare then automatically forwards the claim information to your Medigap insurer. Your Medigap plan pays your 20% share (and any deductibles, depending on your plan letter) directly to the provider. In most cases, you do not need to do anything — the two insurers coordinate automatically. Your EOB will show a $0 balance in the "You may be billed" column if your Medigap plan covered your portion.

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How to access your claims online at medicare.gov

Step 1 — Go to medicare.gov

Open a web browser and type medicare.gov in the address bar. Click "Log in."

Step 2 — Create or sign in to your account

If you do not have an account, click "Create account" and follow the prompts. You will need your Medicare card and personal information to verify your identity.

Step 3 — Navigate to Claims & Appeals

After signing in, look for the "My Account" section or the main menu. Click "Claims & Appeals." You will see a list of all recent claims, sorted by date.

Step 4 — Review a claim

Click on any claim to see the full details: provider name, date of service, what was billed, what Medicare paid, and your responsibility.

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Quick Tip:

Keep a personal log — a notebook or a simple spreadsheet — of every doctor visit, lab test, and medical procedure you have. When your EOB arrives, check each claim against your log. Any discrepancy is worth a phone call to Medicare.

How to Read Your Medicare Explanation of Benefits Letter

Understand what an EOB is (and is not)

Find your EOB — paper or online

Read the four key dollar amounts

Check each claim for errors

Report errors or fraud

Understand your Medigap supplement plan