The first thing to understand is that disputes work. Hospitals negotiate. Billing departments correct errors. Insurers reprocess claims. The reason most people overpay is not that the system is impenetrable. It is that most people do not know what to ask for, or do not ask at all.
The second thing to understand is that you are not disputing out of nowhere. You are disputing against a published set of rules. The Medicare fee schedule, the National Correct Coding Initiative edits, your insurer's explanation of benefits. These are all public documents. When a charge violates them, you have a factual basis for your dispute, not just a complaint.
Here is the sequence, start to finish.
Step 1: Request the itemized bill
You are legally entitled to an itemized bill. Call the hospital billing department and ask for one. Do not accept the summary bill. You need every charge broken out individually, with the CPT or HCPCS code, the date of service, the quantity, and the dollar amount. If you have not done this before, our guide to reading an itemized bill explains every column and what to look for before you start auditing.
In most states this must be provided free of charge. What to do if they push back: Ask specifically for the UB-04 claim form or the 1500 form (for physician bills). These are the standard forms submitted to your insurer and contain all the codes and charges.
Step 2: Request your Explanation of Benefits
Your insurer's Explanation of Benefits (EOB) shows what your insurer was billed, what they agreed to pay, and what they say you owe. This is a separate document from the hospital bill. And the two do not always match.
If you see a service on your hospital bill that does not appear on your EOB, that is a red flag. The insurer may not have been billed for it, or it was submitted under a different code.
Step 3: Identify the errors
With your itemized bill in hand, look for these patterns. We cover each of these in depth, with real CPT code examples and exact dispute language, in our guide to common billing errors.
- Duplicate charges: The same CPT code billed twice on the same date.
- Unbundled codes: Procedures that should be included in a larger code but were billed separately.
- Price outliers: Charges that are two or more times the Medicare rate for the same service.
- Charges for services not received: A physical therapy session on the day you were discharged.
- Incorrect facility fees: Outpatient services billed at hospital outpatient rates when they should have been billed as professional services.
Step 4: Calculate what you should have been charged
For each error you identify, you need a specific number. Not just "this seems high." For price outliers, the reference point is the Medicare Physician Fee Schedule (PFS) rate for your locality. CMS publishes these rates quarterly. For unbundled codes, the reference is the CMS NCCI edit table. For duplicates, the math is simple: you owe for one instance, not two.
Step 5: Write the dispute letter
A dispute letter is more effective than a phone call because it creates a paper trail and triggers a formal review process. Your letter should include:
- Your name, date of birth, account number, and date of service
- The specific CPT code(s) you are disputing and the exact dollar amounts
- The rule or rate being violated (NCCI edit, Medicare fee schedule, duplicate charge)
- The amount you believe you owe (if you can calculate it)
- A request for a written response within 30 days
Sample dispute letter paragraph
"My bill dated [date] includes a charge for CPT 45380 (colonoscopy with biopsy, $380) billed separately from CPT 45378 (diagnostic colonoscopy, $1,240) on the same date of service. Per CMS National Correct Coding Initiative (NCCI) edit guidelines, 45380 is a component code of 45378 when performed in the same session. No modifier is present on my itemized bill. I am requesting removal of the CPT 45380 charge and correction of my balance accordingly."
Send the letter by certified mail or email with a read receipt. Keep a copy. Note the date sent.
Step 6: Follow up and escalate if necessary
Most billing departments have a 30-day review window. If the dispute is not resolved satisfactorily, you have several escalation paths:
- Your insurer's appeals process: If the issue involves incorrect processing of a covered claim, your insurer can intervene directly with the provider.
- Your state insurance commissioner: For balance billing violations or No Surprises Act issues.
- The hospital's patient advocate or ombudsman: Most large hospitals have a patient financial services advocate.
The dispute process itself is not hard. It is just tedious. If the bill is large or complex enough that professional help seems worth it, our guide to medical billing advocates covers what they charge and when the economics make sense.