If your doctor accepts Medicare assignment, they can bill you only your deductible and coinsurance, and anything above the Medicare-approved amount is off limits. If your doctor is "non-participating," Medicare.gov says they can charge more than the approved amount, in many cases up to 15% more; that cap is called the limiting charge. Compare the bill to the "Maximum You May Be Billed" column on your Medicare Summary Notice (MSN), and call the office about any amount above it.
What does "balance billing" mean with Medicare?
Balance billing is when a provider bills you for the difference between their full charge and what Medicare approved. Under Original Medicare, whether a provider can do that depends on how they work with Medicare. There are three kinds of providers:
1. Providers who accept assignment (participating). They agree to take the Medicare-approved amount as full payment. Medicare.gov says they agree to charge you only the Medicare deductible and coinsurance, and they usually wait for Medicare to pay its share before asking you to pay yours.
2. Non-participating providers. They don't accept assignment for every service. They can choose to accept the approved amount case by case. When they don't, they can charge more than the approved amount, up to the limiting charge in many cases. You might have to pay the full amount at the time of service, and they should still submit a claim to Medicare for you.
3. Providers who opted out of Medicare. Medicare won't pay these providers at all except in emergencies. You sign a private contract and pay their price. Your Medigap policy won't pay anything for those services either.
How does the 15% limiting charge work?
The limiting charge means a non-participating provider generally can't bill more than 15% above the amount Medicare approves for them.
Here's an illustrative example with made-up numbers. Say the Medicare-approved amount for a non-participating provider is $100, and you've already met your 2026 Part B deductible of $283.
- Limiting charge: $100 + 15% = $115. That's the most the provider can charge.
- Medicare pays 80% of the approved amount: $80.
- You pay the rest of the $115: $35. That's your $20 coinsurance plus the $15 above the approved amount.
If the same office billed you $160 for that service, the extra $45 would be above the limit.
How do I know if I was billed more than the limit?
Your Medicare Summary Notice (MSN) does the math for you. Find the line for the service and look at the "Maximum You May Be Billed" column. That figure already accounts for whether the provider accepted assignment.
Then compare:
- Bill matches the maximum: Probably correct.
- Bill is lower: A supplement or other coverage may have paid part.
- Bill is higher: Call the provider and ask them to explain each dollar above the maximum.
Also look at the bill for words like "balance due after insurance" next to the provider's full charge. Sometimes an office forgets to post Medicare's adjustment, so the full price stays on your account.
What should I say when I call the billing office?
Have your MSN and the bill ready. You might say:
"Hi, I'm calling about my bill for the visit on [date]. My Medicare Summary Notice shows the Medicare-approved amount was [amount] and the maximum I may be billed is [amount]. Your bill shows [amount]. Do you accept Medicare assignment? Can you check whether Medicare's payment and adjustment were posted to my account?"
If they say they're non-participating, ask: "Is this charge within the Medicare limiting charge for this service?"
Write down the date, the person's name, and what they said. If they agree it's wrong, ask for a corrected statement, and wait for it before you pay. If you already paid too much, ask for a refund in writing.
If the office won't fix a charge that's above the MSN maximum, call 1-800-MEDICARE (1-800-633-4227) and explain what happened.