Around 80% of medical bills contain errors. Not typos — systematic errors that consistently favor the provider or insurer over you. Some are honest mistakes in a genuinely complex system. Others are the predictable output of revenue cycle software that's been optimized, over decades, to maximize charges.
Either way, you're the one who pays.
Here are the seven most common errors — and how to catch them before they catch you.
1. Unbundling
When a provider performs a group of related procedures, they should bill them under a single bundled code at a lower rate. Unbundling is when they bill each component separately, charging you more for the exact same services.
Example: A comprehensive metabolic panel should be billed as one test (CPT 80053). Instead, the lab bills each of the 14 individual components separately — sodium, potassium, glucose — at a higher combined price. Same blood draw. Bigger bill.
How to spot it: Multiple line items that seem related to a single test or procedure. If you had "routine blood work" but see 10+ separate charges, something's wrong.
2. Upcoding
The provider bills for a more expensive service than what was actually performed. This is especially common with office visits, where the difference between a Level 3 and Level 4 visit can be $100+.
Example: You go in for a straightforward 10-minute follow-up — no new symptoms, no procedures. The bill shows a Level 4 or Level 5 office visit (CPT 99214 or 99215), reserved for complex cases requiring detailed examination. You got a check-in. You're paying for a workup.
How to spot it: Compare the visit code on your bill to what actually happened. A routine follow-up shouldn't be billed at the same level as a complex diagnostic evaluation.
3. Duplicate Charges
The same service billed twice. This happens more often than you'd think, especially when care involves multiple departments or handoffs between systems that don't talk to each other.
Example: You get an X-ray in the emergency department. Radiology bills for it. The ED also bills for it. Two charges, one X-ray.
How to spot it: Identical or near-identical line items with the same date of service. Pay attention to charges from different departments for what was clearly a single service.
4. Balance Billing
If you see an in-network provider, they've agreed to accept your insurer's contracted rate. Balance billing is when the provider charges you the difference between their list price and that contracted rate — something they're generally not allowed to do.
Example: The provider's list price is $2,000. Your insurer's contracted rate is $1,200. After insurance pays its share, the provider bills you for the $800 difference. That's not your responsibility — but they'll send you the bill anyway and hope you don't know that.
How to spot it: Compare the "amount billed" on your EOB to the "allowed amount." If you're paying more than your share of the allowed amount after copays, coinsurance, and deductible, you may be getting balance billed.
5. Incorrect Patient Information
Wrong insurance ID, wrong date of birth, wrong policy number. These errors seem minor but they can result in your claim being denied entirely — and you being billed as uninsured at full list prices.
Example: A digit is transposed in your insurance ID when the claim is filed. The insurer rejects it. Instead of resubmitting with corrected information, the provider sends you a bill for the full amount. You're now paying out-of-pocket for a clerical error that wasn't yours.
How to spot it: Verify your insurance information on every bill and EOB. If a claim was denied, check the denial reason first — many are simple data entry errors fixable with a phone call.
6. Out-of-Network Surprise Billing
You chose an in-network hospital, but the anesthesiologist or radiologist who treated you was out-of-network. The No Surprises Act (effective January 2022) generally protects you from these charges for emergency services — but the protections aren't always applied automatically. You have to know to ask.
Example: You have surgery at an in-network hospital. The surgeon is in-network, but the assistant surgeon isn't. You get a separate bill at out-of-network rates for a provider you never chose and may never have met.
How to spot it: Review every provider on your bill, not just the primary one. If any provider is listed as out-of-network for emergency or involuntary services, the No Surprises Act likely applies.
7. Incorrect Modifier Codes
Modifier codes change how a procedure is billed — indicating bilateral procedures, multiple surgeons, or reduced services. A wrong modifier can significantly change the price, and it's one of the hardest errors for patients to catch.
Example: A procedure performed on one side of the body is billed with a bilateral modifier (modifier 50), effectively doubling the charge. Or a reduced-service modifier (modifier 52) is omitted, billing you at full rate for a procedure that was only partially completed.
How to spot it: Look for charges that seem disproportionate to the service you received. This one often requires cross-referencing procedure codes and modifiers on your bill with your EOB — which is exactly the kind of thing software should be doing for you.
What To Do When You Find an Error
Document everything. Keep the original bill, your EOB, and notes about what actually happened during your visit.
Call the provider's billing department. Many errors can be resolved with a phone call — if you know what you're looking for. Ask them to review the specific charges you're questioning and explain any discrepancies.
File an appeal with your insurer if the error involves a denied claim or incorrect processing. You have this right. Use it.
Know your deadlines. Most insurers have appeal windows of 180 days from the EOB date. Don't let the clock run out — that's another thing the system counts on.
The system is complex by design. But the errors in it are knowable, and they're fixable. You just need to know what to look for — or have something that looks for you.
Kupu automatically scans your bills for all seven of these errors and generates the documentation you need to dispute them. Join the beta — it's free