Most people throw away their Medicare Summary Notice.

That’s a mistake.

Every few months, Medicare mails a thick envelope stamped: “This Is Not a Bill.” Because of that line, many people assume it isn’t important. In reality, it may be the single best tool you have to protect yourself from billing errors — and unnecessary charges.

What the Medicare Summary Notice (MSN) Actually Is

The MSN is Medicare’s official record of every service billed in your name over the past 3–4 months.

It shows:

  • What your provider charged
  • What Medicare approved
  • What Medicare paid
  • What you may still owe

It is not a bill — but it tells you whether the bills you receive are accurate and legitimate.

The 4 Columns That Actually Matter

When reviewing the claims section, focus on these four columns:

1. Amount Charged

This is what the provider billed Medicare.

It is often inflated and not the amount you should pay.

2. Medicare-Approved Amount

This is the most important number on the page.

It’s the negotiated rate Medicare allows for that service.

  • If the provider accepts assignment, they generally cannot charge you more than this amount (aside from your share).
  • Some providers may charge slightly more (up to a limited percentage) if they do not accept assignment.

3. Medicare Paid

This is Medicare’s portion — typically about 80% of the approved amount (after any deductible).

4. Maximum You May Be Billed

This is your responsibility.

In many cases, it will be about 20% of the approved amount, unless:

  • You have a supplemental (Medigap) plan
  • You’ve already met your deductible
  • There are special billing circumstances

If this number looks unusually high, it’s worth a closer look.

The Column Most People Miss: “Notes”

Each claim often includes a small letter (a, b, c, etc.).

At the bottom of the page, those letters correspond to explanations in the “Notes for Claim Above” section.

This is where the real story is.

You may see notes like:

“Medicare denied this claim, but you are NOT responsible for paying this charge.”

If you skip this section, you might pay a bill that the provider is legally required to write off.

This happens more often than most people realize.

A Simple 2-Minute Check That Catches Most Errors

When your MSN arrives:

  1. Write down every doctor visit or service you remember from the past few months.
  2. Compare your list to the Services Provided section.
  3. Flag anything you don’t recognize.
  4. Compare the “Maximum You May Be Billed” amount to any bills you’ve received.

If something doesn’t match:

  • Call the provider’s billing department
  • Ask for an itemized bill
  • Do this before paying anything

Most issues can be resolved with a single phone call.

Common Issues This Can Catch

  • Duplicate charges
  • Services you didn’t receive
  • Upcoding (billing for a more expensive service than performed)
  • Charges you are not legally required to pay

You Don’t Have to Wait for the Mail

You can view your claims online at:

👉 http://MyMedicare.gov

Claims often appear there within days of a visit.

This makes it much easier to track down issues early — before bills pile up.

Final Thought

The Medicare Summary Notice may look like paperwork you can ignore.

It isn’t.

It’s a verification tool — one that can save you money, prevent billing mistakes, and protect you from paying charges you don’t actually owe.

Take two minutes to review it. That’s often all it takes.