10 Most Common Medical Billing Errors (And How to Spot Them)

Medical billing errors cost American patients an estimated $68 billion per year. Most go uncontested because patients don't know what to look for. Here are the ten most common mistakes — and the telltale signs on your bill.

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1. Duplicate Charges

High impact

The same service billed twice — sometimes on the same line, sometimes days apart. This is one of the most common and easiest errors to catch. Look for any CPT code that appears more than once on the same date of service.

Example: You receive a blood draw (CPT 36415) billed twice on the same visit. The second charge is pure error.

2. Upcoding

High impact

A provider bills for a more complex or expensive service than what was actually performed. A routine office visit (99213) billed as a complex one (99215) is classic upcoding — the difference can be hundreds of dollars.

Example: You saw your doctor for a 10-minute follow-up but were billed for a comprehensive new patient exam at 3x the cost.

3. Unbundling

High impact

Some procedures are meant to be billed together as a package, which is cheaper. Unbundling means billing each component separately to inflate the total. Medicare and most insurers have specific rules about which codes must be bundled.

Example: A surgical procedure that includes follow-up care is billed with a separate line item for the follow-up, even though it's included in the surgical code.

4. Services Not Rendered

High impact

Charges for procedures, supplies, or consultations that never actually happened. This can range from an honest charting mistake to outright fraud. Always compare your bill to your own memory of the visit.

Example: You're billed for a specialist consultation that was ordered but then cancelled before it happened.

5. Wrong Diagnosis Code

Medium impact

ICD-10 diagnosis codes determine how your claim is classified. A wrong code can make a covered procedure appear non-covered, or cause your claim to be denied. It can also affect your future insurability.

Example: A doctor treats you for a sprained ankle but accidentally codes it as a fracture — triggering different billing and potentially unnecessary follow-up requirements.

6. Balance Billing

High impact

When an out-of-network provider bills you the difference between their charge and what your insurer paid. The No Surprises Act (2022) made this illegal in most emergency situations. You should only pay your normal in-network cost-sharing amount.

Example: An out-of-network anesthesiologist at an in-network hospital sends you a separate bill for $4,000 after insurance pays their portion.

7. Incorrect Patient Information

Medium impact

A wrong date of birth, insurance ID, or even another patient's charges mixed into your bill. These clerical errors can cause claim denials and incorrect charges on your record.

Example: Two patients with similar names in the same hospital. Some charges from one patient's stay end up on the other's bill.

8. Inflated Supply Charges

Medium impact

Hospitals charge wildly varying amounts for supplies — a box of gloves, a saline bag, or a surgical kit. These charges are often many times the actual cost and rarely questioned. Check any line item listed as 'supplies' or 'materials.'

Example: A single-use surgical supply kit billed at $800 when it costs the hospital $40.

9. Operating Room Time Overcharges

High impact

OR time is billed by the minute and is extremely expensive. Rounding up OR time or including prep and cleanup in billable procedure time is a common source of overcharges.

Example: A 45-minute procedure is billed as 90 minutes of operating room time.

10. Miscoded Procedures

Medium impact

Using the wrong CPT code for a procedure — not necessarily to inflate the charge, but due to coder error. The wrong code might result in a higher charge, a denied claim, or a procedure appearing on your record that you never had.

Example: A simple skin lesion removal is coded as a complex excision, doubling the billed amount.

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