Most bills that arrive after Medicare pays are for your share of the cost: the yearly Part B deductible ($283 in 2026) and the 20% coinsurance on the Medicare-approved amount. Other common reasons include a denied service, a provider who doesn't accept assignment, or a supplement plan that hasn't paid yet. Billing mistakes happen too, so compare the bill to your Medicare Summary Notice (MSN) before you pay.
Doesn't Medicare pay the whole bill once it pays?
Original Medicare pays its share and leaves the rest to you or your other coverage. For most Part B services, like doctor visits, outpatient tests, and medical equipment, Medicare pays 80% of the Medicare-approved amount after you meet your deductible. You owe the other 20%.
Medicare's 2026 cost sheet lists the Part B deductible at $283. You pay it once each year before Original Medicare starts paying.
So if you see a doctor early in the year, you may get a bill close to the full approved amount, because it went to your deductible. Later in the year, bills are usually smaller, closer to 20%.
What are the most common reasons for a bill after Medicare pays?
1. Your deductible. Early-year services go toward the yearly deductible first.
2. Your 20% coinsurance. After the deductible, you owe 20% of the approved amount for most Part B services. Original Medicare has no yearly cap on this unless you have supplemental coverage.
3. A denied service. If Medicare decided a service wasn't covered or wasn't medically necessary, you may owe the full charge. Your Medicare Summary Notice (MSN) will show "NO" in the "Service approved?" column.
4. A service Medicare doesn't cover. Medicare doesn't cover things like routine dental care and most hearing aids. If you got one of these, the bill is yours unless other coverage pays.
5. You signed a waiver. Before some services, a provider may ask you to sign an Advance Beneficiary Notice of Noncoverage (ABN), Form CMS-R-131. The Centers for Medicare & Medicaid Services (CMS) says providers give it to people with Original Medicare when they expect Medicare to deny payment, and it shifts potential financial responsibility to you. If you signed one and Medicare denied the service, you'll likely owe the bill. You can read more on CMS's ABN page at cms.gov/medicare/forms-notices/beneficiary-notices-initiative/ffs-abn.
6. Your provider doesn't accept assignment. Medicare.gov says non-participating providers can charge more than the approved amount, in many cases up to 15% more. That extra is called the limiting charge.
7. Your Medigap or other insurance hasn't paid yet. Providers sometimes bill you before your supplement pays its part. Your MSN may say the claim was sent to your supplement plan.
8. Hospital outpatient or observation care. If you were at the hospital as an outpatient, including under observation, Part B rules apply, and you can get separate bills for the hospital and for each doctor.
9. A billing mistake. Duplicate charges, wrong codes, or charging you the full price instead of the approved amount.
How do I tell whether the bill after Medicare paid is correct?
Find the Medicare Summary Notice that covers the same date of service. On the claims page, look at the column called "Maximum You May Be Billed." That's the most the provider can bill you for that service before any supplement or other coverage pays.
Then compare:
- Bill equals the maximum: The bill is likely correct. If you have Medigap, check whether it's been sent there.
- Bill is less than the maximum: Your supplement or another plan probably paid part.
- Bill is more than the maximum: Call the provider. Ask them to explain the difference.
- Service isn't on your MSN yet: The claim may still be processing. You can check your claims in your Medicare.gov account, or call 1-800-MEDICARE (1-800-633-4227).
If you're in a Medicare Advantage plan, use your plan's Explanation of Benefits instead of an MSN. Your share is set by your plan's copays, coinsurance, and deductible.
Why did I get two bills for one hospital visit?
Hospitals and the doctors who treat you there often bill separately. You might get one bill from the hospital and others from the emergency doctor, radiologist, or anesthesiologist. Each one should show up as its own line on your MSN. Match each bill to its MSN line by provider name and date.