Eight out of ten medical bills contain at least one error. That's not a scare tactic — it's what Harvard Medical School found in a 2024 study. The five most common billing errors are duplicate charges, upcoding, unbundling, phantom charges, and balance billing. Most are easy to spot if you know what to look for.
Duplicate Charges
The most common billing error by a wide margin: a service is billed twice — either under the same code or different codes that describe the same thing. You might see a blood draw charged twice on the same day, a room fee duplicated across consecutive days, or an administration fee appearing under two different names.
What to look for: Scan for line items with identical or near-identical descriptions on the same date. If you see "venipuncture" twice, or two separate "laboratory handling" fees within the same visit, flag it.
Example: A patient in Ohio was billed $47 for "blood draw" on a Tuesday and again on Wednesday — but only had one appointment. The second charge was a clerical error from a different billing staff member. Both charges were removed after a single phone call.
How to check: Compare your itemized bill to your appointment calendar. If you only visited once, any repeated service from that visit is a duplicate. Call the billing department and reference the specific line items and dates.
Upcoding
The provider bills for a more expensive procedure than what was actually performed. Each medical procedure has a CPT code — the billing shorthand that insurance companies use. Upcoding happens when a provider substitutes a higher-coded procedure than what occurred, inflating the charge.
What to look for: Compare the CPT codes on your bill to your explanation of benefits (EOB) from your insurance company. Your EOB describes what was performed. If the bill uses a different — usually higher — code than what appears on your EOB, that's a mismatch worth questioning.
Example: A patient received a standard 15-minute office visit (CPT 99213, typically $75–$120) but was billed for an extended visit (CPT 99215, typically $150–$200). The medical record showed a routine checkup — not a complex examination. The billing office corrected the code after the patient shared the discrepancy.
How to check: Request your medical records from the visit and compare the documented procedure to the billed code. Your insurance company's EOB will also show what was "allowed" — which is a clue to what the provider claimed was performed.
Unbundling
Some services are meant to be billed together under a single bundled code. When a provider charges each component separately instead of using the bundled rate, that's unbundling — and it almost always results in a higher total charge.
What to look for: Laboratory panels are a common culprit. A comprehensive metabolic panel (CMP) billed as 14 separate individual tests will cost far more than the same panel billed under the single CMP code. Similarly, surgical bundled codes cover the facility fee, nursing, supplies, and monitoring — charging these separately is improper.
Example: A full lipid panel billed as a single code costs roughly $20–$40. When each component (total cholesterol, HDL, LDL, triglycerides) is billed separately, the same test suite can run $80–$120. A billing advocate identified this pattern in a Texas patient's claim and recovered $340 in unbundling charges.
How to check: Look at whether your lab or procedure could reasonably fall under a bundled code. CMS publishes fee schedules that list which codes are meant to be bundled. The key signal: if multiple line items describe sub-components of the same procedure, ask the billing office whether a bundled code applies.
Charges for Services Not Rendered
Sometimes you'll be billed for a test, procedure, or medication you never received. This can result from clerical errors (a code was entered for the wrong patient), copy-paste billing from prior visits, or — in rare cases — intentional fraud.
What to look for: Any line item you can't explain by referencing your appointment notes, discharge paperwork, or conversation with your provider. Charges for medications you weren't given, equipment that wasn't used, or tests you declined are phantom charges.
Example: A patient in California was billed for a sleep study she never scheduled. The charge appeared on her account because a billing code from a prior patient with a similar name was entered incorrectly. It was resolved after a 20-minute call — but would have gone unpaid if she hadn't read her itemized statement closely.
How to check: Cross-reference every line item against your own records: your appointment notes, discharge instructions, and any takeaway materials from the visit. If you don't recall receiving it, you probably didn't.
Balance Billing
When you receive care from an out-of-network provider at an in-network facility, you may be charged the difference between what the provider billed and what your insurance allowed. This gap is called a balance bill — and without protections, you're on the hook for it.
The good news: The No Surprises Act (2022) protects patients from surprise balance billing in most emergency and scheduled care scenarios at in-network facilities. However, the protections don't cover all situations — ground ambulances, certain elective procedures, and care at out-of-network facilities outside specific scenarios may still be fair game for balance billing.
Example: A patient at an in-network hospital had surgery performed by an anesthesiologist who was out-of-network. The anesthesiologist's bill: $3,200. Insurance allowed: $900. Without No Surprises Act protections, the patient would owe the $2,300 difference. With the Act in force, the provider must accept the insurance rate as payment in full — but only if the patient files a formal dispute.
How to check: Verify the network status of every provider involved in your care — including anesthesiologists, radiologists, and assistant surgeons — not just your primary physician. If you received care at an in-network facility and an out-of-network provider charged you a balance, you may have grounds to challenge it under federal or state law.
Why This Matters
Americans carry over $220 billion in outstanding medical debt. Half of all collection accounts on credit reports come from medical bills — many of which contain errors. You are not helpless in this process. Billing errors are common, recoverable, and frequently resolved with a single well-written dispute letter.
The same Harvard study found that 78% of formal dispute letters result in a reduction or elimination of the erroneous charge. That number tracks with what we see at BillFight. A correctly written letter — citing the specific code violation and the relevant regulation — moves billing departments to act.
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Upload Your Bill — $29Frequently Asked Questions
How do I know if my medical bill has an error?
Start by requesting a full itemized bill from your provider. Compare each line item to your insurance Explanation of Benefits (EOB). Look for duplicates, services you didn't receive, and codes that don't match what was performed. Billing errors fall into five main categories: duplicate charges, upcoding, unbundling, phantom charges, and balance billing.
What is the most common medical billing error?
Duplicate charges are the most common billing error. A service — like a blood draw or an office visit — is billed twice under the same or different codes. They're also the easiest to catch: if a line item appears twice for the same date, that's a duplicate.
How much money can I recover by disputing a billing error?
The average billing error adds $1,200 to a medical bill, according to medical billing advocacy groups. Larger errors — like upcoded surgeries or multi-line unbundling — can mean hundreds to thousands of dollars in overcharges. 78% of formal disputes succeed in reducing or eliminating the erroneous amount.
Is balance billing legal?
In most cases, no — for in-network facilities. The No Surprises Act (2022) protects patients from balance billing by out-of-network providers at in-network hospitals and clinics. However, the protection doesn't cover all scenarios (ground ambulance, certain elective procedures). Always verify whether your provider was in-network at the time of service before paying a balance bill.
What's the fastest way to dispute a medical billing error?
Upload your bill to BillFight. For $29, we generate a professionally written, legally grounded dispute letter tailored to your specific error — ready to print, sign, and mail. Most disputes through BillFight are resolved within 30–45 days.