Explanation of Benefits versus medical bill

Read the EOB in the right order

First confirm the patient, provider, dates, and services. Then find the amount billed, the plan's allowed amount, discounts or adjustments, amount the plan paid, and patient responsibility. Patient responsibility may include deductible, copayment, coinsurance, noncovered services, or another amount explained by a reason code.

An EOB may show a denied or pending claim. Read every remark and appeal instruction before treating the displayed amount as final. A provider bill may arrive before claim processing is complete, so ask the billing office to place the account on hold when the plan is still processing or correcting the claim.

• CMS: how to read an EOB

Worked example with fictional numbers

This example is fictional and is only a reconciliation exercise. A clinic charges $420. The plan's allowed amount is $250, so the contractual adjustment is $170. The EOB says the plan paid $180 and the patient's responsibility is $70. The numbers reconcile: $170 adjustment + $180 plan payment + $70 patient responsibility = $420 billed charge.

If the provider's bill asks for $70 and identifies the same visit, the bill matches the processed EOB. If it asks for $240, do not assume the extra $170 is owed: $240 could incorrectly combine the $70 responsibility with the $170 adjustment. Call the provider and the plan. Real claims may include several service lines, so reconcile each line rather than only the totals.

Use a four-column comparison

For every service line, write down: date and description; EOB patient responsibility; provider payment or credit already posted; and remaining provider balance. Match claim numbers when available. Also check whether the provider name differs because a laboratory, radiologist, anesthesiologist, or other organization submitted a separate claim.

Do not send sensitive records through an unverified email address. Use the phone number on your insurance card, the plan's secure portal, and verified contact details from the provider statement. Keep copies of corrected bills, EOBs, receipts, portal messages, and call reference numbers.

• Print the bill and EOB comparison worksheet

What to ask when the documents do not match

Ask the provider: ‘Has the claim finished processing? Which claim and service line produced this balance? Did you post the plan payment and contractual adjustment? Will you send an itemized statement?’ Ask the plan: ‘Why is this amount assigned to me? Is the provider in network for this claim? Is the claim final, and what is my appeal deadline?’

A mismatch may result from timing, coding, missing insurance information, coordination of benefits, network status, or an actual patient obligation. It does not prove an error by either party. If the issue involves a possible surprise out-of-network bill, use CMS's bill-rights action plan. If it is a coverage denial, follow the appeal instructions in the plan documents.

• CMS medical-bill rights action plans