Start with an itemized bill
A summary bill shows totals by category. An itemized bill lists every individual charge: each procedure, supply, room night, and medication with its code and unit price. Always ask for the itemized version. Hospitals are required to provide it upon request.
Call the billing department and ask specifically for the "itemized statement" or "itemized bill." Get it in writing, not just verbally. If the hospital charges a fee for printing, ask them to waive it or send it by email.
Compare the bill against your Explanation of Benefits
Your insurer sends an Explanation of Benefits (EOB) after processing a claim. The EOB lists every service billed, what the insurer paid, and what you owe. Lay the EOB next to your itemized bill and compare them line by line.
Look for services on the hospital bill that do not appear on your EOB. A service not covered by insurance is not necessarily something you must pay. It could be an unbundled charge, a duplicate, or a service that was never performed.
Common billing errors to look for
Duplicate charges are the most common error: the same service billed more than once under slightly different descriptions or codes. Upcoding happens when a provider bills a more expensive code than the service actually performed. Unbundling occurs when a single procedure is split into multiple codes to increase the total charge.
Other errors include charges for services never received, operating room time that does not match surgical records, and medications billed at retail price rather than the lower wholesale cost hospitals actually pay.
- Duplicate line items for the same service or supply
- Upcoded procedure or room codes (e.g., intensive care when standard care was given)
- Unbundled charges for procedures that should be billed together at a lower rate
- Services marked as performed on dates you were not at the facility
- Medications listed at quantities higher than dispensed
- Operating room time that exceeds the actual procedure duration
Check CPT and diagnosis codes
Every procedure on your bill has a five-digit Current Procedural Terminology (CPT) code. You can look up any CPT code at the American Medical Association website or on the CMS fee schedule to see what it represents. Verify that each code matches the service you actually received.
Diagnosis codes (ICD-10 codes) also matter. If a code is incorrectly assigned, your insurer may deny coverage for a service that should be covered, or you could be flagged for a pre-existing condition you do not have.
What to do when you find an error
Document every error in writing. Note the line item, the code, the amount, and the reason you believe it is incorrect. Contact the hospital billing department first. Many errors are corrected at this stage without a formal dispute.
If the billing department does not resolve the error within 30 days, file a dispute in writing with both the hospital and your insurer. Keep copies of everything. Under the No Surprises Act (effective January 1, 2022), you have specific rights to dispute bills from out-of-network providers for emergency services.
Frequently asked questions
Can I request an itemized bill even after I have already paid?
Yes. You can request an itemized bill at any time. If you find an error after paying, you can still file a dispute and request a refund. Hospitals are required to provide itemized bills upon request regardless of payment status.
How long does a hospital have to correct a billing error?
There is no federal deadline for hospitals to correct billing errors, but most billing disputes are resolved within 30 to 60 days. If you are not getting a response, escalate in writing and contact your state insurance commissioner.
What percentage of medical bills contain errors?
Estimates range from 49% to 80%, depending on the study and the type of bill. A 2021 audit of Medicare claims found improper payments totaling $25.1 billion in a single year, most of which were billing errors rather than fraud.
Do I need to hire a medical billing advocate to find errors?
No, but it helps for complex or large bills. Advocates typically charge 25% to 35% of the amount they recover. For bills under $1,000, a careful review using your EOB and itemized statement is usually sufficient.