How common are medical billing errors?
Healthcare billing is complex. A single hospital stay can generate charges from multiple departments, billed using thousands of procedure codes, processed through insurance systems with their own rules and adjustments. The opportunity for error is significant — and the data reflects that.
Audits of hospital bills have found error rates ranging from 50 to 80 percent, depending on the study and the institution. The American Medical Association has estimated that around one in ten insurance claims contains a coding error. While many mistakes are minor, some result in patients being billed hundreds or thousands of dollars more than they should owe.
The practical implication is straightforward: requesting an itemized bill and reviewing it carefully is not an unusual or adversarial act. It is a reasonable step before paying any significant medical charge.
If you haven't already received an itemized bill — a line-by-line breakdown of every charge — request one from the billing department before reviewing anything. A summary bill showing only a total amount is not enough to identify errors.
The most common types of medical billing errors
Duplicate charges
The same service, supply, or procedure appears on the bill more than once. This can happen when charges from different departments are compiled into a single bill without deduplication, or when a service is entered twice in the billing system. Duplicate charges are one of the most common findings on itemized bill reviews.
Upcoding
A charge is billed at a higher level of service than what was actually provided. For example, a routine office visit billed as a complex evaluation, or a standard procedure billed using a code for a more intensive version. Upcoding can be intentional fraud or a genuine coding mistake. Either way, it results in a higher bill than you should owe.
Unbundling
A group of services that are typically billed together under a single code are instead billed separately, each with its own charge. Since individual codes often cost more than the bundled rate, unbundling inflates the total. Insurers have rules against unbundling, but the practice still appears on bills.
Services not rendered
A charge appears for a service, test, or item that you never actually received. This can include routine items like medications or supplies that are listed as administered but weren't, or consultations from specialists you never saw. Comparing your bill against your own records of the visit is the most reliable way to identify these charges.
Incorrect patient or insurance information
A billing error caused by a wrong insurance ID, incorrect date of birth, misspelled name, or wrong plan number can result in a claim being denied or processed incorrectly — leading to a bill that attributes more to your responsibility than is accurate. These errors often go unnoticed because the bill looks plausible on the surface.
Wrong procedure or diagnosis codes
Medical billing relies on standardized codes — CPT codes for procedures and ICD codes for diagnoses. A transposition, a digit off, or an outdated code can result in a charge that doesn't match what was done, or a denial from your insurer because the procedure doesn't match the stated diagnosis. These errors are not always visible on a summary bill — they require the itemized version.
Balance billing errors
Balance billing occurs when a provider bills you for the difference between their charge and what your insurer paid. In some situations this is legitimate; in others it is not. The No Surprises Act limits balance billing in emergency situations and certain other contexts. If you are being billed an amount that seems inconsistent with what your EOB shows as your patient responsibility, that gap is worth investigating.
Charges for standard inclusions
Some items that appear as separate line charges — basic supplies, routine nursing care, standard medications — may already be included in the facility fee for an inpatient stay. Billing for them additionally is sometimes called "double dipping." These charges can be difficult to identify without an itemized bill and some familiarity with how hospital billing works.
How to check your bill for errors
You do not need specialized knowledge to review a medical bill effectively. A methodical approach covers most common errors.
Step 1: Request an itemized bill
Ask the billing department for a complete itemized bill — every line item, with dates, service descriptions, and billing codes. You are entitled to receive one. Many billing errors are invisible on a summary bill and only become apparent when you see the individual charges.
Step 2: Compare against your records
Check the bill against your own recollection of the visit or stay. Does the date match? Does the list of services match what you remember receiving? Are there providers listed that you don't recognize or didn't interact with? Anything that doesn't align is worth questioning.
Step 3: Compare against your EOB
If your insurer has processed the claim, you will have received an Explanation of Benefits (EOB). Compare the "patient responsibility" figure on your EOB to what your provider is asking you to pay. If the provider's bill is significantly higher than your EOB's patient responsibility, that discrepancy needs an explanation before you pay anything.
Step 4: Look for duplicates
Scan your itemized bill for identical or similar line items appearing more than once on the same date. Duplicate charges can appear under slightly different descriptions, so look at the codes as well as the descriptions.
Step 5: Check the basic information
Verify that your name, date of birth, insurance ID, and plan information are correct on the bill. An incorrect insurance ID can mean your insurer's payment wasn't applied properly, leaving you with a larger balance than you should owe.
If you have questions about a charge, it is reasonable to delay payment while you review. Contact the billing department and let them know you are reviewing the itemized bill. Most providers are accustomed to these requests and will not send your account to collections during a reasonable review period.
What to do when you find an error
Finding a potential error is the start, not the end. Here is how to follow through effectively.
- Identify the specific charge. Note the line item, date, service description, and amount. The more specific you are, the easier it is for the billing department to investigate.
- Contact the billing department in writing. A written communication — even an email — creates a record. State clearly which charge you are questioning and why. Reference your itemized bill and, where relevant, your EOB.
- Ask for a written response. A billing department can verbally tell you a charge has been corrected. Without written confirmation, verify the correction on a revised bill before paying.
- Escalate if necessary. If the billing department does not resolve the issue, ask to speak with a billing manager or the hospital's patient advocate. For insurance-related disputes, contact your insurer's member services line.
- Keep copies of everything. Save your original itemized bill, your EOB, any correspondence, and any revised bills. If a dispute continues, this documentation is essential.
The majority of billing errors are genuine mistakes — not intentional fraud. Billing departments deal with error corrections regularly. A clear, specific, written inquiry tends to produce results more quickly than a general complaint.
When the error involves your insurance
Some billing errors only become visible after your insurer has processed the claim. If your EOB shows your insurer covered less than you expected — or denied coverage entirely — the error may be on the insurer's side rather than the provider's.
Common insurance-side issues include:
- A claim submitted with the wrong procedure or diagnosis code, causing a denial or reduced payment
- A service processed as out-of-network when the provider is actually in-network
- A service denied for lack of prior authorization when authorization was obtained
- A deductible applied incorrectly if you have already met your annual deductible
In these cases, the path forward typically involves contacting both the provider (to correct the claim submission) and the insurer (to reprocess the corrected claim). Most insurers have a formal appeals process if a denial cannot be resolved through standard member services.