Error 1: Duplicate charges
Duplicate charges occur when the same service is billed more than once — either by the same provider or because a service was billed by both the facility and the physician separately as if it were two distinct services. This is the single most common billing error. On a hospital itemized bill, look for the same CPT code listed on multiple dates when you only received the service once, or the same supply item (like surgical gloves or IV tubing) billed multiple times. Compare your itemized bill against your Explanation of Benefits (EOB) — your insurer pays once, but if you're uninsured or have a deductible, you might pay twice without realizing it.
Error 2: Upcoded emergency room visits
ER visits are coded on a 5-level scale (CPT codes 99281-99285) based on the complexity of the visit. Level 5 (99285) is the most complex and most expensive. Studies show that ER billing has shifted dramatically toward Level 4 and Level 5 codes even for routine visits — a practice called upcoding. If you went to the ER for a sprained ankle and were billed at the highest complexity level, that's worth questioning. Ask the billing department for the documentation supporting the level of service billed. If the complexity level doesn't match your records, dispute it.
Error 3: Unbundled procedure codes
Medical billing uses "bundled" codes when multiple related services are performed together — the bundle should be billed as one code at a combined rate. Unbundling is when a provider bills each component separately, generating a larger total charge than the bundled code allows. For example, a comprehensive metabolic panel (CPT 80053) covers 14 tests. If each test is billed individually, the total cost could be 3-4 times higher. A laboratory panel performed during surgery being billed as 12 separate lab tests is a classic unbundling error. Check your itemized bill for groups of procedure codes that correspond to a standard panel or bundled surgical service.
Error 4: Phantom charges for supplies never used
Hospitals sometimes charge for supplies that were prepared but never actually used during your care — like surgical instruments set up on the sterile field as a precaution but not deployed, or medications that were prepared but not administered. These "phantom charges" are most common in surgical and procedural settings. To identify them, request your complete itemized bill and compare it to your medical records. Your anesthesia record, nursing notes, and operative report will document what was actually used. Items in your bill that don't appear in any clinical documentation may be phantom charges.
Error 5: Incorrect diagnosis codes
ICD-10 diagnosis codes determine which services your insurer covers. An incorrect diagnosis code — even a small administrative error — can cause a legitimate claim to be denied. A common scenario: your doctor treats you for a chronic condition, but the billing department uses an "initial encounter" code when you're actually receiving ongoing treatment. Another scenario: a condition is coded as unspecified when your records clearly document the specific type. Incorrect codes can also trigger false flags for pre-existing conditions or affect your future coverage. If your claim was denied for a diagnosis-related reason, ask your provider to review the codes and resubmit with corrected documentation.
Error 6: Out-of-network charges at in-network facilities
The No Surprises Act of 2022 banned most surprise out-of-network billing, but errors still occur. The most common pattern: you receive care at an in-network hospital, but one of the treating physicians — an anesthesiologist, radiologist, pathologist, or hospitalist — is out of network. Before the No Surprises Act, you could be balance billed for the difference. Now, for most covered situations, you should only pay your in-network cost-sharing. If you receive an out-of-network bill for care received at an in-network facility, dispute it and cite the No Surprises Act. The provider cannot balance bill you in most circumstances covered by the law.
Error 7: Wrong patient or wrong insurance information
Administrative errors — wrong member ID, wrong date of birth, misspelled name, wrong insurance company — cause claims to be denied or attributed to the wrong patient. These are simple to fix but can spiral into months of billing confusion if not caught early. When you receive an itemized bill, verify: the name and date of birth match yours, the insurance ID matches your insurance card, the service date is accurate, and the provider name is the correct facility or physician. If any information is wrong, contact the billing department immediately for a correction before the claim is processed.