Medicare Summary Notice (MSN) and EOB Explained
Quick answer: Neither a Medicare Summary Notice nor an Explanation of Benefits is a bill. If you have Original Medicare, Medicare sends you an MSN. If you have a Medicare Advantage or Part D plan, your plan sends you an EOB. Both show the same story in different layouts: what was billed, what was approved, what was paid, and what you may owe. The one number that matters most is the last one. If you owe anything at all, the bill comes separately from your provider, never from the notice itself.
A thick envelope from Medicare lands in the mailbox, full of dollar amounts, and the first instinct is worry. The totals look large, the columns look like a bill, and the natural question is how much to pay and where to send it. The answer, for both of the documents this page covers, is that you pay nothing from the notice itself. That single fact calms the panic, but it leaves the real work undone: checking that every service listed is one you actually received, that the amount your provider can bill you matches what the notice allows, and that nothing was denied that should have been paid. This page decodes both documents, column by column, and gives you the steps for when something on them is wrong.
One timing change makes this page more urgent than it would have been a year ago. Since January 2026, paper MSNs arrive only every 6 months, where they used to come every 4 months. A fraudulent charge can now sit unnoticed for half a year if you only read the paper version. The fix for that is in the online section below, and it costs nothing.
Which paper are you holding?
Three Medicare documents look alike and do different jobs. A fourth, the ANOC, arrives in the same fall mail and gets mixed in with them. Identify yours first, because the sender, the schedule, and the appeal path all depend on it.
| Document | Who sends it | When it comes | What it is |
|---|---|---|---|
| Medicare Summary Notice (MSN) | Medicare | Paper every 6 months since January 2026, only if you had services in that period; electronic version monthly | The claim summary for Original Medicare, Parts A and B |
| Explanation of Benefits (EOB) | Your Medicare Advantage or Part D plan | Monthly or quarterly, depending on the plan | The claim summary for a private plan, in that plan's own layout |
| Evidence of Coverage (EOC) | Your Medicare Advantage or Part D plan | Each fall, by October 15 | The full rulebook for your plan: what it covers, what you pay, and your appeal rights |
| Annual Notice of Change (ANOC) | Your Medicare Advantage or Part D plan | Each fall, by September 30 | Only what is changing next year; our ANOC guide covers it in full |
If you have Original Medicare and no private plan, you will only ever get an MSN, never an EOB. If you have a Medicare Advantage plan, you will get an EOB from that plan instead of an MSN. If you have Original Medicare plus a standalone Part D plan, you get both: an MSN for your Part A and B claims and a Part D EOB for your prescriptions. If a document arrives from the wrong sender for your coverage, that alone is worth a phone call to Medicare at 1-800-633-4227 before you trust anything on it.
Reading your MSN, column by column
Every MSN follows the same format, which is good news: once you learn it, every MSN you ever get reads the same way. The front of the notice summarizes the period: your deductible status, an overview of your claims and costs, and the providers you saw. Then comes the claim-by-claim table, which is where the money lives. For Part B services, the columns are:
| Column | What it means in plain words |
|---|---|
| Service and date | What the provider did, and when. Check the date first: a wrong date can mean someone else's claim landed on your record. |
| Amount charged | What the provider billed. This is the provider's price, not what you owe. |
| Medicare-approved amount | What Medicare considers a fair price for that service. This is the number everything else is calculated from. |
| Medicare paid | What Medicare actually paid the provider. |
| Maximum You May Be Billed | The most the provider can bill you for that service. This is the most important column on the notice. It can include deductibles, coinsurance, and noncovered charges, and the provider may not bill you more than this amount. |
Part A notices, for hospital stays, follow a similar layout with approved amounts and your potential responsibility. After the claims table, the MSN has a notes section that explains any denial in more detail, and the last page carries the appeals information: how and when to ask for a review, with step-by-step directions. Keep the notice until you have verified every claim on it, and shred it before throwing it away, since it lists your health services and your Medicare number.
One detail worth knowing: your MSN shows your Medicare number, the 11-character Medicare Beneficiary Identifier on your red, white, and blue card. It does not show your Social Security number. The old system that used Social Security-based numbers is gone. A supposed Medicare notice that shows or asks for a Social Security number is not following the format of a real one.
Reading your EOB
An EOB tells the same story as an MSN, but each plan designs its own, so the headings, the order of the columns, and the amount of detail vary. Do not worry if your EOB looks nothing like a neighbor's EOB from a different plan. That is normal. Look for the same four ideas under whatever headings your plan uses: what the provider billed, what the plan approved, what the plan paid, and what you may owe. If your EOB says you may owe money, the same rule applies as with an MSN: the bill comes separately from your provider.
Part D EOBs have one extra job. They track your prescription drug costs through the year, so they are the place to watch your progress toward your plan's coverage stages and out-of-pocket totals. If a drug you take every month suddenly shows a different amount, check the EOB's notes for a tier change or a coverage rule before assuming a billing error. Your plan's member portal usually shows EOBs sooner than the mailed version, and your plan must send a paper copy if you ask for one.
The 4 checks that take five minutes
Put the notice beside any bill from the same provider and run these four checks. Most problems surface in the first two.
1. Is every service yours? Read down the service list and confirm you received each one, on the date shown, from the provider shown. A service you never received, a provider you have never seen, or equipment you never ordered is the single most important thing an MSN or EOB can reveal. It can be a billing error, or it can be fraud using your Medicare number.
2. Does the provider's bill match the notice? Compare what the provider billed you against the Maximum You May Be Billed column on an MSN, or the amount-you-may-owe column on an EOB. The provider may not bill you more than that amount. If you already paid the provider, check that what you paid matches the notice. If you paid more, contact the provider's billing department and ask for a refund of the difference.
3. Was anything denied, and why? Denied claims appear with a reason in the notes section. Common reasons are coding errors, missing information, or a service Medicare or the plan does not cover in that situation. A denial is not the final word. The appeals section below explains the next step, and the deadline on it matters.
4. Are there duplicates or wrong dates? The same service appearing twice, or a date that does not match your appointment, is one of the most common billing mistakes. Flag it the same way you would flag an unknown service: a call to the provider's billing department resolves most of these.
If something is wrong: the order that works
Step 1: call the provider's billing department. Many errors are simple mistakes, and the provider can often fix them by correcting the information and resubmitting the claim. This is the fastest resolution for coding errors, wrong dates, and duplicates, and it costs nothing to try first.
Step 2: appeal, if the provider cannot fix it. For Original Medicare, the first level of appeal is called a redetermination. You have 120 days from the date you receive the MSN to ask for one, and Medicare presumes you received the notice 5 days after the date printed on it, so do not let the deadline drift. File using form CMS-20027 or the instructions on the last page of your MSN, and send it to the address on the notice. You will generally get a decision within 60 days. Our Letter Explainer includes an MSN redetermination template that walks through the same request. For a Medicare Advantage or Part D denial, the appeal goes through your plan instead, and your plan's denial notice gives the deadline and the steps. Do not apply the 120-day MSN rule to a plan denial. The plan's own deadline controls.
Step 3: report it as fraud, if the service never happened. If your notice shows a charge for a service or supply you did not receive or order, and the provider cannot explain it, report it. Call Medicare at 1-800-633-4227, the HHS Inspector General hotline at 1-800-447-8477, or your state's Senior Medicare Patrol at 1-877-808-2468 for free help. This step matters more than it used to, because the paper notice now comes only every 6 months. In March 2026, the Oklahoma Insurance Department reported that 12 Oklahomans on Medicare had found charges on their notices for more than 15,000 urinary catheters they never ordered, totaling over $135,000 in charges, of which Medicare had already paid $88,793. Every one of those charges was visible on a notice. The people who caught them were the people who read them.
Do not wait six months: check claims online
The 6-month paper cycle is the weakest part of the current system, and the fix is free. If you create an account at Medicare.gov, you can view your Part A and Part B claims as they are processed, often within a day, instead of waiting for the paper notice. You can also sign up for electronic MSNs: then you get an email with a link to your MSN for any month in which you have a processed claim, instead of one paper notice every 6 months. If you have a Medicare Advantage or Part D plan, your plan's member portal is the equivalent shortcut for EOBs. None of this requires giving your Medicare number to anyone who contacts you. You open the account yourself, at Medicare.gov or your plan's own site, typed into your browser.
If you do not use the internet, the paper notice still works, and the phone still works. Call Medicare at 1-800-633-4227 and ask for a copy of any notice, or ask for help reading one. The Senior Medicare Patrol number above, 1-877-808-2468, connects you with free local help in every state.
Scam guard: what a real notice never does. A real MSN or EOB never asks you to pay Medicare, never asks for your bank account, Medicare number, or Social Security number by phone, text, or email, and never threatens you. A message claiming you owe Medicare money, demanding payment through a link or a gift card, or asking you to confirm your Medicare number to release a notice is not following any real process. Verify the claim yourself at Medicare.gov or by calling 1-800-633-4227, and never use a phone number or link that arrived inside the suspicious message. Our Medicare calls guide covers the call version of this trick, and our scam recovery guide covers what to do if you already shared details.
One more seasonal note. The fall mail brings the EOC and the ANOC alongside these claim notices, and Open Enrollment runs from October 15 to December 7. That pile of plan mail is prime cover for impersonators, so the same rule applies to all of it: read the paper, verify through channels you open yourself, and ignore any message that adds urgency or a payment demand to a real document. Our Open Enrollment scams guide covers the seasonal versions.
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Check It Now — Free →Is a Medicare Summary Notice a bill?
No. A Medicare Summary Notice is a summary of the services and supplies that providers billed to Medicare during a period, what Medicare paid, and the maximum amount you may owe the provider. It is not a bill. If you owe anything, your provider bills you separately. Never send a payment to Medicare based on an MSN.
What is the difference between an MSN and an EOB?
An MSN comes from Medicare itself and covers Original Medicare, Parts A and B. An EOB comes from your private plan and covers Medicare Advantage or Part D. Both show what was billed, what was approved, what was paid, and what you may owe, and neither one is a bill. EOB layouts vary by plan, while every MSN follows the same format.
How often will I get an MSN?
Since January 2026, paper MSNs arrive every 6 months, and only if you had services or medical supplies during that period. Before that change, paper MSNs came every 4 months. If you sign up for electronic MSNs, you get one for any month in which you have a processed claim, so the electronic version arrives much sooner.
I lost my MSN. How do I get another copy?
Log in to your Medicare account at Medicare.gov, where you can view your claims and MSNs, or call Medicare at 1-800-633-4227 and ask for a paper copy to be mailed to you.
How long do I have to appeal a denied claim on my MSN?
You have 120 days from the date you receive the MSN to ask for a redetermination, which is the first level of appeal for Original Medicare. Medicare presumes you received the notice 5 days after the date printed on it. File using form CMS-20027 or the instructions on the last page of your MSN.
My EOB looks nothing like my neighbor's EOB. Is that normal?
Yes. Each Medicare Advantage and Part D plan designs its own EOB, so the layout, headings, and order of the columns differ from plan to plan. The columns still mean the same things: what was billed, what was approved, what the plan paid, and what you may owe.
Sources: Medicare.gov, Medicare Summary Notice (MSN); Centers for Medicare and Medicaid Services, First Level of Appeal: Redetermination by a Medicare Contractor; U.S. Department of Health and Human Services, Level 1 Appeals: Original Medicare, Parts A and B; Center for Medicare Advocacy, Medicare Summary Notices (MSNs) Mailings Reduced to Six Months, March 2026; Oklahoma Insurance Department, consumer alert on Medicare catheter supply billing, March 23, 2026; Medicare and You Handbook 2026 (Evidence of Coverage delivery). Last updated October 2026.