Medical Bill Audit Checklist: 12 Things to Check (2026)

The average American hospital bill contains multiple line items that are worth questioning — from duplicate charges and incorrect codes to inflated facility fees and services that were never provided. BillKarma's analysis of thousands of hospital bills finds potential billing issues in approximately 1 in 4 bills reviewed. The difference between patients who catch errors and those who do not often comes down to one thing: a systematic review. This 12-point checklist is the same process professional medical billing advocates use, adapted so you can do it yourself in 30 to 60 minutes.

1. Before you start: get the right documents

You need three documents before you can audit your bill effectively:

1. Itemized bill with CPT codes. Call the billing department and request an itemized statement showing every individual charge with its CPT or HCPCS code, date of service, description, quantity, and dollar amount. If the hospital sends you a summary (e.g., "Lab Services: $1,200"), call back and ask specifically for the line-item detail.
2. Explanation of Benefits (EOB). This comes from your insurance company and shows what was billed, what insurance paid, adjustments, and your patient responsibility. If you have not received it, download it from your insurer's patient portal or call member services.
3. Your personal records. Notes you took during your visit or stay, discharge paperwork, prescriptions, and any recollection of what medications you received, which doctors saw you, and what tests were performed. These are your reality check against what the bill claims happened.

With these three documents in hand, work through the checklist below. Each check takes 2 to 5 minutes. The entire audit should take 30 to 60 minutes for a typical bill. Or, if you want to skip the manual work, upload your bill to BillKarma and our analyzer will run all 12 checks automatically.

2. The 12-point audit checklist

Now let us walk through each check in detail.

Check 1: Verify patient information

Look at the top of your bill for your name, date of birth, address, and insurance information. A single wrong digit in your insurance ID, an incorrect date of birth, or a misspelled name can cause your insurance claim to be denied — which means the full charge comes to you. Example: A patient's insurance ID was entered as 123456789 instead of 123456780. The claim was denied, and the patient received a $6,400 bill. A two-minute phone call to the billing department corrected the digit, the claim was reprocessed, and the patient owed $840.

Check 2: Check dates of service

Verify that every date on the bill matches your actual treatment dates. For hospital stays, check the admission and discharge dates against your discharge paperwork. Hospitals sometimes bill for the discharge day or include an extra day. Example: A patient was discharged at 9 a.m. on a Thursday but billed for room and board through Thursday night — an extra $1,840.

Check 3: Match CPT codes to services received

Look up each CPT code on your bill to verify it matches the service you actually received. You can search any CPT code at our calculator. Pay special attention to imaging codes (did you get a CT with or without contrast?), surgical codes (was the correct procedure billed?), and evaluation codes (does the visit level match your experience?). Example: A patient had a CT without contrast (CPT 74176, Medicare rate ~$122) but was billed for CT with contrast (CPT 74178, billed at $2,400). The correct code billed at the hospital's rate would have been $1,600 — a $800 overcharge from the wrong code alone.

Check 4: Look for duplicate charges

Sort your bill by date and CPT code. Look for the same code appearing on the same date without clinical justification. Duplicates are especially common on multi-day stays where billing systems may log charges from different departments independently. Example: A complete blood count (CPT 85025) billed once by the lab and once by the nursing floor for the same date — a $280 duplicate.

Check 5: Verify insurance was billed correctly

Check whether the bill reflects insurance processing. If you see the full gross charge with no insurance adjustment or "insurance pending," your insurance may not have been billed. This can happen when the provider has outdated or incorrect insurance information. Example: A patient received an $8,000 bill with no insurance adjustment. The provider had the patient's old insurance on file. Once the correct insurer was billed, the patient's responsibility dropped to $1,600.

Check 6: Check the math

Add up every line item on the bill and compare to the stated total. Billing systems occasionally produce math errors, or adjustments may not be reflected in the total. This takes five minutes with a calculator and catches errors that no one else is checking for. Example: A bill with 14 line items totaling $3,840, but the stated total was $4,340 — a $500 discrepancy traced to an adjustment that was not applied.

Check 7: Compare bill to your Explanation of Benefits

Your EOB shows what your insurance company processed. Compare the patient responsibility on the EOB to the amount on the provider's bill. If they do not match, one of them is wrong. The most common discrepancy: the provider bills you for the full charge before insurance has finished processing, or the provider does not reflect an insurance adjustment that the EOB shows. Example: EOB shows patient responsibility of $1,200 after insurance paid $3,800. Provider bill shows $2,400 patient responsibility — the $1,200 difference was an in-network discount that the billing department had not applied.

Check 8: Check for unbundling

Unbundling means billing component procedures separately when a single bundled code should cover all of them. The bundled code is always cheaper. CMS publishes NCCI edits listing over 200,000 code pairs that cannot be billed together. Example: A colonoscopy with biopsy correctly billed as CPT 45380 (Medicare: $198). Unbundled, it might appear as CPT 45378 (colonoscopy) plus a separate biopsy code — each with its own charge, totaling more than the bundled rate.

Check 9: Verify units and quantities

Check that the number of units on each line item matches what you actually received. Medications are particularly prone to unit errors — billed for four doses when you received two, or billed at a higher dosage than administered. Example: A patient received 2 units of IV ondansetron (anti-nausea) but was billed for 4 units. At $85 per unit, that is a $170 overcharge.

Check 10: Check facility fees

Hospital-owned physician practices can charge a facility fee on top of the professional fee — sometimes called a "site-of-service" charge. This is legal but can double your cost compared to a freestanding office. Verify whether the facility fee is legitimate and whether your insurance covered it. You can look up your hospital's billing grade in our directory to see how its facility fees compare to regional averages. Example: A routine office visit at a hospital-owned clinic billed as 99214 ($128 professional fee) plus a separate facility fee of $340 — total $468. The same visit at a freestanding office: $128 total.

Check 11: Look for upcoding

Upcoding means billing for a higher-cost service level than was actually performed. The most common example is ER visit levels: a straightforward visit billed at Level 5 instead of Level 3. Compare the billed visit level to the complexity of your actual experience. Example: A patient visited the ER for a minor laceration requiring three stitches. The bill showed CPT 99285 (Level 5, billed at $4,800). The patient requested a coding review, and it was downgraded to 99283 (Level 3, billed at $1,200) — a $3,600 reduction.

Check 12: Compare charges to Medicare rates

Medicare rates are a useful benchmark for what a procedure should cost. While hospitals charge more than Medicare pays, the ratio gives you a negotiation reference point. A charge that is 10 to 15 times the Medicare rate is worth questioning. Use our calculator to look up any CPT code:

3. Annotated bill example with flagged items

Here is a sample hospital bill for a 2-day stay after an appendectomy, with the 12-point checklist applied. Five items are flagged:

The five flagged items total $3,578 in potentially incorrect charges: a duplicate CBC ($284), an extra room-and-board day ($1,940), three extra medication units ($255), and a cardiology consultation that may not have occurred ($620). Each of these would be caught by the corresponding checklist item. Scan your own bill with BillKarma to get a similar flagged report with Medicare rate comparisons for every line item.

4. What to do after your audit

1. Document every flagged item. For each potential error, note the date, CPT code, charge amount, and which checklist item it failed. Be specific — "CBC billed twice on 02/10, $284 each" is better than "duplicate charge found."
2. Call the billing department. Reference each flagged item by date and CPT code. For simple errors (duplicates, wrong patient info, math errors), a phone call often resolves it on the spot.
3. Follow up in writing for anything not resolved in 10 days. Send a written dispute listing each item. Include your account number, the specific charges in question, and supporting documentation (your EOB, discharge papers, personal notes).
4. Request a formal billing review. Ask the hospital to conduct a formal coding review for any items involving upcoding, unbundling, or medical necessity questions. This triggers an internal audit process. If the hospital is nonprofit, they are also required to screen you for financial assistance before pursuing collections.
5. Do not pay disputed amounts. Ask for the disputed charges to be placed on hold during the review. Pay the undisputed portion if you can, but do not pay charges you are actively disputing. For letter templates and escalation steps, see our dispute guide.

5. Case study

6. Frequently asked questions

7. Sources

• HHS Office of Inspector General: Medicare Fee-for-Service Improper Payment Rate — Annual Audit Results
• CMS: National Correct Coding Initiative (NCCI) Edits — Unbundling Prevention and Code Pair Reference
• CMS: Medicare Physician Fee Schedule — 2026 CPT Code Rates and Relative Value Units
• Medical Billing Advocates of America: Patient Bill Audit Outcomes and Savings Data
• AARP: How to Read and Dispute a Medical Bill — Consumer Guide
• KFF: Americans’ Challenges with Health Care Costs — Billing Error Prevalence and Impact