Medical billing is one of the most error-prone processes in any industry. A study by the Medical Billing Advocates of America found that up to 80% of medical bills contain at least one error. These aren't always small mistakes — some can add hundreds or thousands of dollars to your bill.
Here are the seven most common errors to look for, and what to do when you find one.
1. Duplicate Charges
This is the most common billing error: the same service billed twice. It can happen because of a data entry mistake, a system error, or because a service spans two billing periods and gets counted in both.
What to look for: Scan your itemized bill for the same CPT code appearing more than once on the same date of service. Also check for identical charges on consecutive days that might represent one service split across a billing cycle.
What to say: "I see CPT code [X] billed twice on [date]. Can you explain why this service appears more than once?"
2. Upcoding
Upcoding happens when a provider bills for a more expensive service than was actually performed. For example, billing a 99215 (high-complexity office visit) when the visit was actually a 99213 (low-complexity). The difference can be $200 or more for a single visit.
Upcoding can be unintentional — a coder selects the wrong code — or in some cases deliberate fraud. Either way, you can dispute it.
What to look for: If an ER visit or office visit charge seems unusually high, look up the specific E&M code (99201–99215 for office visits, 99281–99285 for ER visits) and compare the complexity level to what you remember about the visit.
What to say: "I was billed for code 99285 (high complexity ER visit), but based on my records, the visit was for [your reason]. Can you review whether this code is correct?"
3. Unbundling
Certain groups of procedures are supposed to be billed together under a single "bundled" code at a lower rate. Unbundling means billing each component separately, which adds up to more than the bundled price.
For example, a surgical procedure might include pre-op preparation, the surgery itself, and immediate post-op care — all covered under one code. Billing these as three separate line items is unbundling.
What to look for: Multiple procedure codes on the same date, especially for things that logically go together (pre-op, procedure, post-op). This is particularly common on ER visit bills and surgical procedure bills.
4. Wrong Patient Information
If your insurance information is entered incorrectly — wrong policy number, wrong date of birth, wrong name spelling — your claim can be denied or processed at a higher cost. These errors are surprisingly common, especially in emergency situations where information is collected quickly.
What to look for: Check the patient information section of your bill and Explanation of Benefits carefully. Verify your date of birth, policy ID, and group number match your insurance card.
5. Services Not Rendered
Occasionally, bills include charges for services that simply weren't provided. This might be equipment that was ordered but not used, a consultation that was scheduled but didn't happen, or medications that were listed in the chart but not administered.
What to look for: Cross-reference your bill with any notes you took during your visit. If you kept a hospital stay journal or had a family member with you, compare the bill against your memory of what actually happened.
What to say: "I see a charge for [service] on [date], but I don't believe that service was provided. Can you confirm this was actually rendered?"
6. Operating Room Time Overcharges
OR time is billed in 15-minute increments, and the clock is supposed to start when the patient enters the OR and stop when they leave. Overcharging for OR time is a frequent and costly error — particularly relevant on knee replacement and childbirth bills where OR time can run thousands of dollars.
What to look for: If you had surgery, check whether the anesthesia time and OR time are consistent with each other and with what you were told. They should roughly match.
7. Incorrect Modifier Codes
Modifier codes are 2-digit additions to CPT codes that indicate something specific about how a service was delivered (e.g., bilateral procedure, multiple surgeons, unusual circumstances). Incorrect modifiers can significantly change the reimbursement amount.
A common abuse is adding modifier -25 (significant, separately identifiable E&M service) to every office visit whether or not there was truly a separate evaluation, allowing double-billing for the visit and a procedure.
What to look for: Any CPT code with a modifier (shown as a dash and two digits, like 99213-25). Ask the billing department to explain what the modifier means and whether it applies to your situation.
How to Dispute a Billing Error
When you find an error:
- Write it down — document the specific code, date, and what you believe is wrong
- Call the billing department — ask to speak to a billing specialist, not general customer service
- Be specific — cite the exact code and your reason for disputing it
- Follow up in writing — send an email or letter summarizing the dispute after your call
- Escalate if needed — if unresolved, contact your state insurance commissioner or a patient advocate
Most legitimate errors are corrected once you flag them. Providers don't want the liability of an intentional billing error on record.
For a step-by-step guide on what to say once you've found an error, see how to negotiate a hospital bill.
Upload your bill to HaggleCare to automatically scan for potential overcharges and get a personalized dispute and negotiation script.