How to Check Your Medical Bill for Errors (Step-by-Step)

To check your medical bill for errors, request an itemized bill with CPT codes from the provider, get your Explanation of Benefits (EOB) from your insurer, then compare the two line by line. Look for duplicate charges (the same code billed twice on the same date), bundling violations (procedures billed separately that should be combined), upcoding (a higher-complexity code than the service you received), charges for services that never happened, and totals that don't match your EOB. You can check any two procedure codes against the government's bundling rules using our free NCCI code pair checker, and look up what Medicare pays for any code with our CPT code lookup tool.

Why does this matter? Up to 80% of medical bills contain errors according to the Medical Billing Advocates of America, and a 2022 JAMA Health Forum study found that roughly 1 in 3 insured patients who reviewed their bills identified a problem. Medical billing errors add up to an estimated $210 billion in annual overcharges across the U.S. healthcare system. The good news: you can catch most errors yourself, without a medical billing degree and without paying anyone. This guide walks you through every step.

What percentage of medical bills have errors?

Medical billing errors are far more common than most patients realize. The numbers are striking:

• 80% of medical bills reviewed by the Medical Billing Advocates of America contained errors. This is the most widely cited figure in the industry, based on their audits of thousands of hospital bills.
• 1 in 3 insured patients who reviewed their medical bills found a problem, according to a 2022 study published in JAMA Health Forum. That number only counts patients who actually looked -- many never check.
• 26% of hospital bills contain at least one incorrect charge, according to a NerdWallet/Harris Poll survey of over 2,000 adults.
• $210 billion in annual overcharges flow through the U.S. healthcare billing system each year, according to estimates from Access One and Becker's Hospital Review.
• $1,300 is the average overcharge on a hospital bill that contains errors, based on data from medical billing advocates and patient advocacy organizations.

These errors aren't limited to complex surgical bills. Simple office visits, lab work, and outpatient procedures are just as likely to have mistakes. A single duplicated blood panel can add $200-$500 to your bill. An upcoded ER visit can cost you $800 or more beyond what the correct charge would have been.

The bottom line: if you don't check your medical bill, there's a good chance you're paying more than you should.

What are the most common medical billing errors?

Before you start checking your bill line by line, it helps to know exactly what you're looking for. These are the 10 most common types of medical billing errors, ranked roughly by how frequently they occur:

• Duplicate charges. The same procedure code billed twice on the same date of service. This is the single most common billing error. It often happens when a charge is entered manually and the billing system doesn't catch the duplicate. For example, a CBC blood test (85025) appearing on two separate lines for the same day.
• Unbundling / NCCI violations. Procedures that should be billed together at a bundled rate are instead billed separately at higher individual rates. CMS maintains over 190,000 code-pair rules (called NCCI edits) that define which codes must be bundled. For example, a comprehensive metabolic panel (80053) already includes a basic metabolic panel (80048) -- billing both is a bundling violation that inflates your bill by $30-$80.
• Upcoding. Billing a higher-complexity (more expensive) procedure code than what was actually performed. A 10-minute office visit for a sore throat is a level 3 E/M visit (99213, ~$110), not a level 4 (99214, ~$170) or level 5 (99215, ~$230). Upcoding is especially common on ER bills, where the difference between level 1 and level 5 can be over $1,000.
• Wrong patient information. Misspelled name, wrong date of birth, incorrect insurance ID number, or wrong subscriber information. These errors can cause claim denials that get passed to the patient as a bill. Always verify the patient demographics section before paying.
• Incorrect quantities. Lab tests billed for more units than were actually performed, or medication doses listed as multiple administrations when only one occurred. Check that the units column matches what you actually received.
• Balance billing violations. Billing patients for amounts beyond what the insurer allows. If your provider is in-network, they've agreed to accept the insurer's allowed amount. If they're billing you more than the "patient responsibility" on your EOB, that may be illegal balance billing -- especially for emergency services under the No Surprises Act.
• Incorrect date of service. Charges assigned to the wrong date, which can cause claims to be denied or result in double billing if the correct date is also billed. Check every date against your own records of when you received care.
• Services not rendered. Charges for procedures, tests, or supplies that simply never happened. This is more common on multi-day hospital stays where many charges are generated. If your bill shows a test or procedure you don't remember receiving, ask for the clinical documentation to support that charge.
• Wrong place of service code. An outpatient procedure billed with an inpatient place-of-service code (or vice versa). This can dramatically change the reimbursement rate and your cost share. Hospital outpatient is code 22; a physician's office is code 11. An office visit coded as a hospital encounter will cost you more.
• Facility fee errors. Hospital-owned clinics often add a facility fee on top of the professional fee, sometimes doubling the total cost. If you visited a doctor's office that happens to be owned by a hospital system, check whether a facility fee was added and whether it was disclosed to you before service.

Before you start: get the right documents

You need two things to check your bill properly:

1. An itemized bill from the hospital or provider -- not the summary statement. The itemized version shows every charge with a CPT/HCPCS procedure code, date of service, quantity, and individual price. You have the legal right to request one. The summary bill (the one most providers send first) just shows a total amount due -- it's useless for catching errors.
2. Your Explanation of Benefits (EOB) from your insurance company -- this shows what your insurer approved, what they paid, and what you owe. If the provider's bill doesn't match your EOB, that's your first red flag. Your EOB is available online through your insurer's portal or mailed to you after each claim is processed.

If you only have a summary bill with a single total, call the billing department and say: "I'm requesting a fully itemized statement with CPT codes for all charges." They must provide it. For a full breakdown of every field on an itemized bill, see our guide on how to read an itemized medical bill.

If you had a hospital stay, also request your medical records for the admission. The clinical record will show which procedures were actually performed, how long your surgery took, which medications were administered, and what tests were ordered. This is your evidence if a charge doesn't match what actually happened.

How do I check my medical bill in 5 steps?

What other errors should I watch for?

Upcoding

Upcoding is when a provider bills a higher-level (more expensive) code than the service actually provided. For example, billing a level 4 office visit (99214, ~$170) when a level 3 visit (99213, ~$110) was actually performed. The difference between E/M levels is based on the complexity of medical decision-making, the number of problems addressed, and the amount of data reviewed. A straightforward visit for a single, stable condition (like a prescription refill or a follow-up for controlled blood pressure) should not be coded at a high complexity level. Upcoding is especially prevalent in ER bills (where visit levels range from 99281 to 99285, with a price difference of $50 to $2,500+) and mental health bills (where therapy session codes are time-based and 30-minute sessions are sometimes coded as 60-minute).

Facility fees

Hospital-owned clinics often charge a "facility fee" on top of the provider's professional fee -- sometimes doubling the total cost. A routine office visit that costs $150 at an independent physician's office can cost $300-$500 at a hospital-owned clinic because of the added facility fee. If you visited a doctor's office that happens to be owned by a hospital system, check whether a facility fee was added. In many states, hospitals are required to disclose facility fees before providing service. If you weren't informed in advance, you may have grounds to dispute the charge. Ask whether the same service is available at a non-hospital-owned location -- it's almost always cheaper.

Operating room time

Surgical bills often include charges for operating room time in 15-minute increments. The hourly rate for an operating room can range from $1,500 to $3,000 or more, so errors in the recorded start/end times can add hundreds or thousands of dollars. If you had a procedure, check that the billed time is reasonable for the surgery performed. A standard arthroscopic knee surgery takes about 30-45 minutes of OR time -- if your bill shows 90 minutes, request the operative report to verify. For procedure-specific guidance, see our guides on knee and hip replacement billing and colonoscopy billing errors.

Anesthesia units

Anesthesia is billed in time units (one unit per 15 minutes) plus a base unit value that varies by procedure. Overcharges often come from incorrect time calculations or using the wrong base units for the procedure. For example, anesthesia for a knee arthroscopy has a base value of 3 units. If your surgery took 45 minutes of anesthesia time, that's 3 time units plus 3 base units = 6 total units. If the bill shows 8 or 10 units, there's likely a time recording error. Compare the billed anesthesia time to what your surgical and anesthesia records indicate.

How long do I have to dispute a medical bill?

Timing matters. Here are the key deadlines you need to know:

• No Surprises Act disputes: You have 120 days from receiving the initial payment notice to initiate the federal Independent Dispute Resolution (IDR) process for surprise out-of-network bills.
• Insurance appeals: Most insurers allow 180 days from the date of a claim denial to file an internal appeal. After that, you can request an external review. Check your specific plan documents -- some allow longer.
• State timelines vary: Many states have their own dispute and appeal timelines that may be more generous than federal rules. Some states allow up to 1 year. See our state-by-state medical bill rights guide for your state's specific deadlines.
• Statute of limitations on medical debt: This ranges from 3 to 10 years depending on your state. This is how long a provider can legally sue you to collect. It does not mean you can't dispute the bill -- you can dispute at any time.
• Credit reporting: Medical debt cannot appear on your credit report until it is at least 365 days past due, giving you time to resolve disputes before any credit impact.

Practical tip: start your dispute within 30 days of receiving the bill for the best results. The sooner you raise the issue, the more likely the billing department is to correct it quickly. Once a bill goes to collections, the process becomes significantly harder.

What to do when you find an error

1. Document everything. Write down the specific charge, the CPT code, the date, and why you believe it's an error. Note the specific billing rule that was violated (e.g., "NCCI edit pair 80053/80048"). Take screenshots of your EOB. Keep a log of every phone call -- date, time, the name of the person you spoke with, and what they said.
2. Call the billing department. Start with a phone call. Reference the specific line item and ask them to review it. Many errors are corrected with a single call. Use our free call script builder to prepare what to say before you call. Be polite but specific -- vague complaints get nowhere.
3. Send a written dispute. If the phone call doesn't resolve it, send a formal dispute letter via certified mail. Include your account number, the specific charges you're disputing, the regulatory basis for your dispute, and a request for a corrected bill within 30 days. Our dispute letter guide has a ready-to-use template, or you can generate a dispute letter automatically using our free tool.
4. Contact your insurer. If the provider doesn't cooperate, contact your insurance company's member services. They have leverage that individual patients don't -- they can reprocess the claim, audit the provider, or apply contractual penalties for billing violations.
5. File a complaint. For unresolved disputes, file a complaint with your state's insurance commissioner or the CMS No Surprises Act helpline at 1-800-985-3059. For Medicare patients, contact 1-800-MEDICARE. State regulators take billing complaints seriously and can compel providers to correct errors.

The key to a successful dispute is specificity. Don't say "my bill is too high." Say "CPT code 80048 on line 4, dated 01/15/2026, is an NCCI bundling violation with CPT 80053 on line 3. Per CMS NCCI edits, these codes cannot be billed together. I am requesting a corrected bill with the bundled code only."

Can medical debt affect my credit score?

Yes, but there are important protections in place as of 2023-2024:

• 365-day waiting period: Medical debt cannot appear on your credit report until it is at least 1 year old. This gives you time to resolve billing disputes, negotiate with providers, or apply for financial assistance before any credit impact.
• Paid medical debt is removed: As of 2023, all three major credit bureaus (Equifax, Experian, TransUnion) remove paid medical debt from credit reports. If you pay a medical collection, it comes off your report.
• Debt under $500 excluded: Medical debt under $500 is excluded from credit reports entirely, regardless of whether it's paid or unpaid.
• 15 states ban medical debt on credit reports: As of 2026, the following states have passed laws restricting or banning medical debt from credit reports: California, Colorado, Connecticut, Illinois, Indiana, Maryland, Minnesota, Nevada, New Mexico, New York, North Carolina, Oregon, Rhode Island, Vermont, and Washington. If you live in one of these states, medical debt may not appear on your credit report at all, regardless of the amount.

The bottom line: you have more time and more protection than you think. Don't let fear of credit damage pressure you into paying a bill you haven't checked. Dispute first, pay only what you actually owe.

Know your rights

• Right to an itemized bill: Federal law gives you the right to an itemized statement from any healthcare provider. This is non-negotiable -- if a provider refuses, file a complaint with your state's health department.
• No Surprises Act (2022): Protects you from surprise bills for emergency services and out-of-network providers at in-network facilities. It also caps your cost share for these services at in-network rates.
• Fair Debt Collection: Medical debt cannot appear on your credit report until it's at least 365 days old. Paid medical debt is removed from credit reports entirely.
• Charity care: Most nonprofit hospitals are required to have financial assistance programs. If you're struggling to pay, ask about their Financial Assistance Policy (FAP) before paying anything. Many hospitals will reduce or eliminate bills for patients below 200-400% of the federal poverty level.
• Price transparency: As of 2021, hospitals are required by CMS to publish their standard charges online in a machine-readable file. As of 2023, insurers must provide personalized cost estimates through price comparison tools. Use these before scheduled procedures to avoid surprises.
• State-specific protections: Many states have balance billing laws, prompt pay requirements, and medical debt protections that go beyond the federal baseline. See our state-by-state guide for details.

When should I hire a medical billing advocate?

Most billing errors can be resolved on your own using the steps in this guide. But there are situations where a professional medical billing advocate is worth the cost:

• Bills over $5,000 with suspected errors. The larger the bill, the more likely there are multiple errors, and the higher the potential savings. A billing advocate's fee is usually a percentage of what they save you, so the math works better on larger bills.
• Complex surgical bills with 50+ line items. Multi-day hospital stays, major surgeries, and ICU bills can have hundreds of individual charges. A professional advocate knows exactly which codes to cross-check and which modifiers to question.
• Denied claims you believe should be covered. If your insurer denied a claim and your internal appeal was unsuccessful, a billing advocate or patient advocate can navigate the external review process and knows how to frame appeals in terms insurers respond to.
• Out-of-network surprise bills. Even with the No Surprises Act, navigating the IDR process can be complicated. An advocate can handle the paperwork and negotiate with both the provider and insurer.
• Typical cost: 25-35% of savings recovered. Most billing advocates work on a contingency basis -- they take a percentage of the money they save you. If they don't save you anything, you don't pay. Some charge a flat fee of $100-$300 for a bill review.

Check your bill yourself first. Use the 5-step process in this guide and our free NCCI checker, CPT lookup, and bill math checker before paying for professional help. Many errors -- especially duplicates, bundling violations, and math mistakes -- are straightforward to catch on your own.

For a deeper dive into every type of billing error and how the billing system works, see our complete guide to medical billing errors. For step-by-step dispute instructions that apply to any bill type, see how to dispute any bill. We also have procedure-specific guides for ER visits, ambulance bills, childbirth hospital bills, MRI and CT scans, physical therapy, mental health, colonoscopy, and knee/hip replacement. If your insurer denied a claim incorrectly, see our insurance billing errors guide.

Frequently asked questions