Most people assume medical bills are accurate. They're not always.
Quick answer
The seven most common are duplicate charges, incorrect quantities, upcoding, unbundling, charges for services you never received, date-of-service errors, and insurance processing mismatches. To catch them, request a fully itemized bill, then read it beside your EOB and circle anything that appears more than once or that you do not recognise.
Medical billing is a chain of handoffs, providers, coders, billing departments, insurance processing. With that many steps, mistakes slip in regularly. The good news: you don't need to be an expert to catch the most common ones. You just need to know what to look for.
Once you spot an error, learn how to dispute it with your hospital or provider.
The 7 most common medical billing errors
Duplicate charges
The same lab test, medication, or supply appears twice on the same bill.
Incorrect quantity
You're billed for 4 units of something you received once, or supplies charged by the bag when you used a fraction.
Upcoding
A more expensive billing code is used than what was actually provided. A routine visit gets coded as a complex one.
Unbundling
Services that should be billed together as a package are split into individual charges to inflate the total.
Charges for services you didn't receive
It happens, especially with busy ER visits or multi-day hospital stays where items get added by mistake.
Date-of-service errors
A charge appears for the wrong day, or for a date outside your actual visit or admission window.
Insurance processing mismatches
Your bill says you owe $2,400. Your EOB says you owe $900. Both can't be right.
The next step is a phone call, a hold queue, and a supervisor who has heard it before. That part we do for you, and only charge if the bill comes down.
Let us make the callThe 10-minute “catch it fast” method
Grab:
- Your bill (ideally itemized, learn how to request an itemized bill)
- Your EOB from your insurer if you're insured (how to read an EOB)
- A pen or highlighter
Then work through it:
- Circle anything that appears more than once
- Flag any quantities that seem off
- Highlight anything you don't recognize or remember receiving
- Compare the total you owe to what your EOB says you owe
- Spot-check the biggest line items against your hospital's published prices, hospitals are required by federal law to post them on their website (search “[hospital name] standard charges”)
- Write down 3-5 questions to ask the billing department
That's it. Most errors jump out quickly once you know what you're looking for. When you want to go deeper, price benchmarks, the full red-flag checklist, and what to do with each find, our step-by-step guide to catching overcharges on a medical bill walks the complete audit. If something looks wrong, use this phone script to dispute it. If a call doesn't resolve it, follow up with a written medical bill dispute letter. For particularly complex bills from surgical procedures, the investigation gets more detailed. Other bill types have their own common errors too, for example, ambulance bills are frequently overcharged for ALS-vs-BLS level of service and inflated mileage, and anesthesia bills are billed in base units plus time units, so an inflated time count is easy to miss and easy to check.
Already paid a bill before spotting the error? You're not out of luck, here's how to get your money back after paying a medical bill.
If you want the done-for-you version
Agent Loop does all of this automatically. You upload your bill and our clever fox investigates, scanning line by line for every error type above, then negotiating directly with your provider.
You don't make calls. You don't decode billing codes. You just get the outcome. No savings, no fee.
Sources
- HHS Office of Inspector General, Physician relationships with payers
Submitting a claim certifies the payment was earned. Improper claims include billing for services not rendered and upcoding, meaning codes reflecting a more severe illness or more expensive treatment than was actually provided.
- AMA, CPT billing codes overview
The CPT code set is a listing of five-digit codes describing medical services and procedures, maintained by the independent CPT Editorial Panel appointed by the AMA Board of Trustees.
- HHS Office for Civil Rights, Your medical records
HIPAA gives you the right to inspect and receive a copy of your medical and billing records, and a provider may not withhold copies over an unpaid bill or charge search and retrieval fees.
- Duffy, Frasco and Trish, JAMA Health Forum, August 2024
Of adults who received a bill they disputed or could not afford, 61.5% contacted the billing office; among those, 25.7% had the bill corrected, 15.2% got a price reduction and 8.1% got financial assistance. Nationally representative survey of 1,135 adults, 2023.
Sources last checked 27 July 2026. Medical billing rules change, so if you spot something out of date, tell us and we will correct it.
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