The billing errors worth checking for are charges for care you didn't get, duplicate charges, wrong codes, bills that ignore what Medicare or your other insurance paid, and charges above the amount Medicare allows. The Centers for Medicare & Medicaid Services (CMS) and the Consumer Financial Protection Bureau (CFPB) both list these kinds of mistakes in their consumer guides. The fastest way to catch them is to compare each bill with your Medicare Summary Notice (MSN) or your plan's Explanation of Benefits (EOB) before you pay.
Where should I start when I check a medical bill?
Gather three things for the same date of service:
- The bill from the doctor, hospital, or lab.
- Your MSN (Original Medicare) or EOB (Medicare Advantage or other insurance).
- Any notes, appointment cards, or receipts from the visit.
If the bill only shows a total, ask for an itemized bill. CMS's "Check your medical bill for errors" guide lists that as the first step.
What billing errors should I look for?
These are the problems CMS and the CFPB tell consumers to watch for, plus a few that are specific to Medicare.
1. Charges for care you didn't get
A test that was ordered and then canceled. A medication you refused. A visit on a day you weren't there. The CFPB's 2024 advisory opinion on medical debt collection lists services not received as amounts a collector can't collect. CMS suggests asking for your medical records and comparing them to the bill. If a charge isn't documented in your records, ask the billing office about it.
2. Duplicate charges
The same service billed twice on the same date. CMS tells consumers to make sure they weren't billed twice for the same service. Some repeats are legitimate, like two separate lab draws, so ask before you assume.
3. The wrong code, or a more expensive code
Every service has a billing code. If the code describes something bigger or more complex than what you had, you can be overcharged. The CFPB's 2024 advisory opinion calls this "upcoding": billing for services more expensive than what the patient actually received. CMS suggests looking up each code by searching it along with the words "medical billing code" and comparing the description to the care you got.
4. Insurance payments missing from the bill
The CFPB suggests checking whether the bill reflects what your insurance paid. A common version: the provider sends a bill showing the full charge before Medicare's payment and adjustment are posted. Compare the "amount you owe" on the bill to "Maximum You May Be Billed" on your MSN.
5. A bill above the Medicare limit
If your provider accepts Medicare assignment, Medicare.gov says they agree to charge you only the deductible and coinsurance. A non-participating provider can charge more, but in many cases no more than 15% above the Medicare-approved amount. If a bill is higher than the MSN maximum, that's worth a call.
6. Bills you already paid
The CFPB suggests first making sure you haven't already paid the bill. Check for copays you paid at the front desk that never got credited.
7. Billed to the wrong insurer, or not billed at all
A CFPB presentation on wrongful bills for older adults lists claims filed with the wrong insurer or not filed at all, incorrect billing codes, untimely filing, missing claim data, and authorization problems as sources of inaccurate bills. If the office has old insurance information or didn't send the claim to your Medigap plan, you may get a bill you shouldn't.
8. Wrong dates, names, or details
The CFPB suggests checking that the charges reflect the services you received. Also check the patient name and Medicare Number. Mix-ups between family members with similar names do happen.
9. Out-of-network labels that aren't right
The CFPB suggests checking whether any charge is marked "out-of-network" when it wasn't. This matters most for people in Medicare Advantage plans with networks.
What's the difference between a billing error and fraud?
Many errors are honest mistakes: a wrong code, a missed payment, a duplicate entry. Fraud is billing on purpose for things that didn't happen. Medicare's notice lists examples like billing you for Medicare services you didn't get.
Call the provider first. If the explanation doesn't make sense, or the provider is one you never visited, report it to 1-800-MEDICARE (1-800-633-4227).