Medical billing runs through a long chain of manual entry, complex coding rules, and software handoffs between the provider, the biller, and the insurer — and errors are common enough that reviewing an itemized bill before paying is a reasonable, ordinary thing to do, not an accusation against anyone. Most billing departments deal with correction requests regularly. Here are the five patterns that account for the majority of what people actually find.
1. Duplicate charges
The same service, test, or supply billed more than once for the same date. This is the easiest error to catch and usually the easiest to get corrected, since it doesn't require any judgment about medical necessity — either the line appears twice or it doesn't.
What it looks like: two identical lines — same code, same description, same date — like "IV insertion (36000) — $85.00" appearing twice on an ER bill.
How to catch it: scan for repeated codes and descriptions on the same date of service. If there's a legitimate reason for two of the same thing (two separate IV lines were actually placed), the billing department should be able to confirm that specifically.
2. Unbundling
Certain groups of tests or procedures are meant to be billed together under a single "bundled" code, at a bundled price. Unbundling is when the individual components get billed separately instead — sometimes as a genuine coding mistake, sometimes because separate line items add up to more than the bundled code would have.
What it looks like: a Basic Metabolic Panel (CPT 80048) billed on the same date as separate charges for glucose, sodium, and potassium — three tests that are already components of that panel.
How to catch it: if you see a "panel" or bundle code alongside separate line items that sound like they could be its components, that combination is worth asking about directly.
3. Upcoding
Billing for a more complex, more expensive version of a service than what was actually performed — for example, billing a Level 4 emergency room visit (a more serious, resource-intensive visit) when the actual visit was closer to a Level 2 or 3.
What it looks like: harder to spot than the others, since it's about the level of a code rather than an obviously wrong line. A large facility fee relative to what felt like a brief, simple visit is the most common tip-off.
How to catch it: compare the visit level code and description against what you remember happening — how long you were there, how many people saw you, what was actually done. If it sounds like a lot more than what you experienced, ask the billing department to explain what justified that level.
| Error type | What to look for |
|---|---|
| Duplicate charge | Same code/description repeated on the same date |
| Unbundling | A panel code plus its own individual component tests |
| Upcoding | A visit-level code that seems higher than what happened |
| Wrong quantity | Units billed that don't match what you remember receiving |
| Phantom charge | A service you don't recall receiving at all |
4. Incorrect quantity
A billed quantity that's implausible for the visit — sometimes a simple data-entry mistake (a "1" becomes an "11"), sometimes reflecting a discrepancy between what was ordered and what was actually given.
What it looks like: 12 tablets of a medication billed for a single ER visit, when a typical visit would involve one or two doses administered on-site.
How to catch it: for any line with a quantity greater than 1, ask yourself whether that many units makes sense for a single visit. If not, it's a specific, easy question to put to the billing department.
5. Charges for services you don't recall receiving
Sometimes called "phantom charges" — a line item for something that either didn't happen, was ordered but canceled, or belongs to a different patient entirely (a genuine, if uncommon, mixup in a busy facility).
What it looks like: a test or procedure on the bill that you have no memory of, especially one unrelated to why you sought care in the first place.
How to catch it: read through every line, not just the expensive ones, and ask about anything you can't place. It's a completely normal question — providers deal with it regularly, especially after a busy ER visit where a patient may not remember everything that happened.
BillCheck scans your itemized bill for exactly these five patterns and drafts the letter to send to billing — $10.99 for one bill, no subscription, nothing stored after your review.
Check your bill →What to do once you've found one
Put it in writing, reference the specific line item by code and description, and ask for a review or correction — not an accusation, just a request for clarification. Most billing departments have a standard process for this. See our companion guide on how to read an itemized bill for the full walkthrough of what each line actually means.