The 12 Most Common Hospital Billing Errors

Why billing errors are so common

Hospital billing is one of the most administratively complex systems in any industry. A single inpatient stay can involve dozens of individual charge entries — from room and board to every medication administered, every procedure performed, every supply used. Each charge requires a specific billing code drawn from a system of over 70,000 diagnosis codes (ICD-10) and over 10,000 procedure codes (CPT codes published by the American Medical Association).

Hospital billing departments are staffed by human coders working under significant volume pressure. Even experienced coders make errors. And because the financial incentive runs in one direction — toward higher charges, not lower — errors almost always result in overbilling rather than underbilling.

The starting point for identifying any of these errors is the itemized bill — the complete line-by-line record of every charge. Most patients only receive a summary statement. You must specifically request the itemized bill from your hospital's billing department, and in most states, hospitals are legally required to provide it.

The 12 most common billing errors

1. Duplicate charges

The same service, medication, or supply is billed more than once. This can occur when two departments enter charges independently, when a procedure is billed by both the hospital facility and the physician group, or when a daily recurring charge is entered for an extra day. Duplicate charges are among the most straightforward errors to dispute because they are unambiguous — the same code appears twice with no clinical justification.

2. Upcoding

Upcoding occurs when a provider assigns a higher-level billing code than the service actually warranted, resulting in a higher charge. The most common example involves evaluation and management (E&M) codes — a Level 3 office visit billed as a Level 5. Emergency department facility fees are particularly prone to upcoding: CMS defines five levels of ED complexity, and billing Level 5 when Level 3 was appropriate is a systematic practice at some facilities. The benchmark for comparison is CMS's Medicare Physician Fee Schedule.

3. Unbundling violations

Medicare and most insurance contracts require related services to be billed together under a single bundled code rather than billed separately at individual rates. Billing them separately — unbundling — inflates the total charge significantly. CMS's Outpatient Code Editor identifies bundling requirements, but hospitals don't always follow them. Surgical procedures and anesthesia services are particularly prone to unbundling.

4. Phantom charges

Charges for services, supplies, or medications that have no corresponding entry in your clinical record — meaning they were never administered or performed. These charges can be identified by comparing your itemized bill against your medical records, which you have the right to obtain under HIPAA.

5. Incorrect patient information

Errors in name, date of birth, insurance ID number, or policy group number can cause claims to be rejected by insurers and ultimately charged to the patient. These administrative errors are easily corrected but frequently go unnoticed.

6. Wrong diagnosis codes (ICD-10 errors)

An incorrect ICD-10 diagnosis code can cause your insurer to classify a service as not medically necessary, resulting in a denial — and ultimately a charge to you. Diagnosis codes must accurately reflect the documented clinical reason for the service.

7. Operating room time overcharges

Surgical procedures are billed in part based on operating room time. If the documented OR time on your bill exceeds the time documented in your surgical records, the overage is a billing error. Operating room charges are typically among the highest individual line items on a surgical bill.

8. Observation status misclassification

Hospitals can classify patients as either "inpatient" or "outpatient under observation." This distinction has major financial consequences, particularly for Medicare patients — observation status does not count toward the three-day qualifying stay required for Medicare skilled nursing facility coverage. Medicare's guidance on observation services outlines patients' rights to be notified of their status.

9. Incorrect room and board rates

Daily room charges vary by unit type — intensive care, step-down, medical-surgical. Patients are sometimes billed at ICU rates for days spent in lower-acuity units. Compare the daily rate on your bill against your admission records and any transfer documentation.

10. Medication overcharges

Hospitals routinely charge retail or marked-up prices for medications that cost a fraction of the billed amount. Medications should also only be billed for doses actually administered, as documented in the medication administration record. Discrepancies between medication charges and administration records are a common finding in bill audits.

11. Services billed by the wrong provider

In hospital settings, services are sometimes billed by a provider who didn't actually perform them — for example, a procedure billed under an attending physician's code when a resident performed it unsupervised. Billing rules for teaching hospitals are specific and frequently violated.

12. Insurance processing errors

Even when the hospital bills correctly, your insurer can process the claim incorrectly — applying the wrong benefit tier, failing to recognize a provider's network status, or incorrectly calculating your cost-sharing. These errors appear on your Explanation of Benefits (EOB) as discrepancies between what the hospital billed, what your insurer paid, and what you owe. Comparing your EOB against your itemized bill is essential.

How to identify these errors yourself

Start by requesting your complete itemized bill from the hospital's billing department. Request it in writing and keep a copy of your request. Then request your medical records for the same dates of service — specifically nursing notes, the discharge summary, and the medication administration record.

Compare every charge on the itemized bill against your medical records. Every charge should correspond to a documented service. Cross-reference procedure codes against Medicare's published fee schedule to assess whether the code level is appropriate for the documented service.

This process is time-consuming and requires familiarity with billing codes. For complex bills — particularly those involving surgery, extended hospitalizations, or ICU stays — the volume of line items and the technical nature of the coding make a professional audit significantly more effective.

Found something that doesn't add up? Get a free consultation — our case managers conduct a full audit of your bill at no cost.

What to do when you find an error

Document the error precisely — note the specific line item, the charge, the code, and why you believe it is incorrect. Then submit a formal written dispute to the hospital's billing department. Written disputes must be responded to; verbal complaints do not create a record.

Include supporting documentation: your medical records, the relevant section of your itemized bill, and — where applicable — the Medicare fee schedule rate for the procedure. Request written confirmation of receipt of your dispute and follow up in writing if you don't receive a response within 30 days.

If the hospital disputes your dispute and you believe your position is correct, you can escalate to your state's insurance commissioner, CMS (for Medicare patients), or — for No Surprises Act violations — the federal Independent Dispute Resolution process.