How to Read a Medicare EOB (Explanation of Benefits)

What Is a Medicare EOB?

A Medicare Explanation of Benefits (EOB) — officially called a Medicare Summary Notice (MSN) — is a statement Medicare sends you after a doctor, hospital, or other healthcare provider submits a claim for services you received. It is not a bill. It's a summary that shows what Medicare was billed, what Medicare paid, and what you may owe.

You'll typically receive an MSN every three months, covering all claims processed during that quarter. If you use Medicare Advantage (Part C), your plan sends its own version of an EOB.

The Key Sections of Your Medicare EOB

1. Header Information

At the top you'll find your name, Medicare number (now a random Medicare Beneficiary Identifier, or MBI, not your Social Security number), and the date range the notice covers. Double-check that the name and number match yours — errors here could mean someone else's claim landed on your account.

2. Claims Summary Table

This is the main section. For each healthcare service you received, you'll see columns showing the date of service, the provider name, a description of the service, the amount billed by the provider, the amount Medicare approved, the amount Medicare paid, and the amount you may owe.

Key thing to understand: The "amount billed" is almost always higher than what Medicare actually approves. Medicare has set rates for every service, so they only "approve" a specific amount regardless of what the provider charges. You generally owe based on the approved amount, not the billed amount.

3. Claim Status Codes

Next to each claim, you may see codes or short messages explaining the payment decision. Common ones include "Claim Approved" (Medicare paid their share), "Claim Denied" (Medicare did not pay — and the notice should explain why), and "Deductible applies" (you haven't met your annual deductible yet, so this cost is on you).

4. Deductible and Coinsurance Tracking

Your MSN often includes a running total of how much of your annual deductible you've used. For Original Medicare (Part B), the annual deductible changes each year. Once you've met it, Medicare typically covers 80% of approved services and you pay 20% (your coinsurance).

5. Appeals and Rights Section

Near the bottom, your EOB explains your right to appeal if you disagree with a coverage decision. You typically have 120 days from the date of the MSN to file an appeal. This section tells you how to start the process and where to send your appeal.

Common Medicare EOB Terms Decoded

Red Flags to Watch For

Review every EOB you receive. Look for services you don't remember getting — this could indicate billing errors or even fraud. Check that the dates and provider names are correct, and make sure the amounts in the "You May Be Billed" column roughly match what your doctor's office charges you. If something seems wrong, contact both the provider and Medicare.

What to Do If a Claim Is Denied

Don't panic — denied claims can often be resolved. First, read the reason code on your EOB carefully. Sometimes it's a simple coding error the provider can fix by resubmitting. If you believe the service should be covered, you have the right to appeal. Start by calling 1-800-MEDICARE (1-800-633-4227) for guidance, or follow the appeal instructions on your MSN.

Skip the Confusion — Decode It Instantly

Reading an EOB shouldn't require a medical billing degree. If you have a Medicare EOB, insurance letter, or any confusing document sitting in front of you right now, you can upload it to Letter Lens and get an instant plain-English breakdown with action items and deadlines highlighted automatically.