What Is an EOB (Explanation of Benefits)?

A mysterious document arrives in the mail after a doctor visit, filled with dollar amounts and insurance jargon, stamped with “This Is Not a Bill.” If you have ever tossed one of those aside, you have thrown away one of the most useful financial tools your insurance provides. An EOB, or Explanation of Benefits, is a detailed statement from your health insurer showing what was billed, what the plan paid, and what you owe. Independent analyses and consumer-advocacy groups have long estimated that a large share of medical bills contain errors — and your EOB is the first place to catch them.

What an EOB Is (and What It Is Not)

What is an EOB at its core? It is a summary your insurance company generates every time a healthcare provider submits a claim on your behalf. The EOB explains how the claim was processed: the total amount billed, the insurer’s negotiated discount, the portion the plan covered, and the amount you are responsible for paying.

Critically, an EOB is not a bill. You do not send payment to your insurer based on the EOB. Instead, it serves as a receipt and verification tool. The actual bill comes separately from the provider’s office, and the amount on that bill should match the “patient responsibility” section of your EOB. If it does not, that discrepancy is worth investigating. For context on specific cost-sharing terms you will see on your EOB, review our guides on copays and coinsurance.

How to Read an EOB: Section by Section

While formatting varies by insurer, most EOBs contain the same core sections. Here is what each one means.

Patient and Provider Information

The top of the EOB lists your name, member ID number, the date of service, and the provider who submitted the claim. Verify this information first — billing errors sometimes occur because a claim was filed under the wrong patient or for the wrong date.

Claim Number

Each processed claim is assigned a unique claim number. Note it down: if you ever need to call your insurer or file an appeal, referencing the exact claim number is the fastest way to get to the right record.

Service Description and Billing Codes

Each service is described with a CPT (Current Procedural Terminology) code and a brief description. You might see entries like “Office Visit — Level 3” or “Complete Blood Count.” If a code looks unfamiliar or you do not remember receiving that service, flag it for follow-up.

Amount Billed

This is the total amount the provider charged before any insurance adjustments. These “sticker prices” are often significantly higher than what anyone actually pays. A routine office visit might be billed at $250 even though the negotiated rate is $120.

Plan Discount / Adjustment

This shows the difference between the billed amount and your insurer’s negotiated rate. In-network providers have agreed to accept this reduced rate, so the adjustment is written off. You do not owe this amount.

Amount Paid by Plan

This is the portion your insurer paid directly to the provider. If you have not yet met your deductible, this amount may be $0, and the full negotiated rate falls to you.

Patient Responsibility

The bottom line — literally. This section shows what you owe, broken down into deductible amounts, copays, and coinsurance. The total here should match the bill you receive from the provider.

Why You Should Always Review Your EOB

Most people file their EOBs away without reading them. That is a costly habit. Here are specific errors to watch for:

• Duplicate charges: The same service billed twice, which is surprisingly common after lab work or multi-day hospital stays
• Services you did not receive: A procedure code that does not match what actually happened during your visit
• Incorrect coding: A provider billing at a higher-complexity level than the service delivered (known as “upcoding”)
• Out-of-network processing for in-network care: A claim processed at out-of-network rates even though the provider is in your plan’s network
• Denied claims that should be covered: Services your plan covers being marked as denied due to missing information or coding errors

Claim denials are common across commercial insurers, and many denials are reversible through appeals — but you cannot appeal what you do not notice. The American Medical Association has documented that a meaningful share of claims are initially denied or processed incorrectly, which is exactly why a two-minute EOB review pays off.

What to Do If Your EOB Shows an Error

Start by calling the customer service number printed on the EOB. Have the document in front of you and reference the specific claim number and service date. Common resolutions include:

If the provider billed incorrectly, the insurer will ask the provider to resubmit the claim with corrected codes. If the insurer processed the claim incorrectly — for example, applying out-of-network rates to an in-network provider — they will reprocess it. Either way, do not pay the provider’s bill until the EOB reflects the correct amounts.

For denied claims, ask the insurer for the specific reason code. Often, a denial results from a missing referral, a prior authorization that was not obtained, or a simple clerical error. Your provider’s billing department can usually resolve these by resubmitting with the correct information. If a covered service stays denied, you have the right to file a formal appeal — the EOB or your plan documents explain the deadline and the steps.

EOB vs. Medicare Summary Notice (MSN)

An EOB and a Medicare Summary Notice do the same job — they explain how your coverage handled your claims — but they come from different places, and which one you receive depends on your coverage.

• If you have Original Medicare (Part A and Part B), you do not get a commercial EOB. Instead, Medicare mails you a Medicare Summary Notice (MSN), typically every three months (quarterly) if you had claims during that period — not after every single visit. The MSN lists the services billed, what Medicare approved and paid, and what you may owe. Like an EOB, it is clearly labeled “This is not a bill.”
• If you have Medicare Advantage (Part C) or a Part D drug plan, your private plan sends you EOB-style statements instead of the MSN, because a private insurer — not Medicare directly — is processing your claims.
• If you have commercial or marketplace insurance, you receive a standard EOB from your insurer, usually shortly after each claim is processed.

You can also view Medicare claims sooner — without waiting for the quarterly MSN — by logging in to your account at Medicare.gov. Whichever document you receive, the review habit is the same: match the services listed against the care you actually received, and check the amount you are told you owe before paying anything.

EOBs and Your Tax Records

Your EOBs serve as documentation for medical-expense tax deductions. Under current IRS rules, unreimbursed medical expenses exceeding 7.5% of your adjusted gross income are deductible if you itemize. Keeping your EOBs organized by year gives you an accurate record of what you paid, which is more reliable than trying to reconstruct costs from credit card statements. Tax rules can change, so confirm the current threshold and requirements with the IRS or a tax professional before filing.

EOBs also help you track progress toward your annual deductible and out-of-pocket maximum. While your insurer tracks these amounts, errors do happen. Comparing your running total against the insurer’s records ensures you are not paying more than your plan requires.

EOBs and Coordination of Benefits

If you have more than one insurance plan — for example, your own employer plan plus coverage as a dependent on a spouse’s plan — your EOBs become more complex. Coordination of benefits (COB) determines which plan pays first (primary) and which pays second (secondary). The primary plan processes the claim first and generates an EOB showing its payment. That EOB is then forwarded to the secondary plan, which may cover some or all of the remaining balance.

Review EOBs from both plans carefully. Errors in coordination of benefits are common and can result in incorrect patient responsibility amounts. If your secondary plan denies a claim because it did not receive the primary plan’s EOB, you may need to manually submit the primary EOB to the secondary insurer for reprocessing.

Digital EOBs and Online Access

Most major insurers now offer electronic EOBs through their member portals and mobile apps. Digital EOBs are typically available within a few days of a claim being processed, while paper versions may take two to four weeks. Signing up for electronic delivery makes it easier to review claims promptly and catch errors while the details of your visit are still fresh.

Some insurers also offer claim alerts — email or text notifications each time a new claim is processed. Enabling these alerts is a simple way to stay on top of your healthcare spending without waiting for documents to arrive.

Frequently Asked Questions

How long should I keep my EOBs?

Keep EOBs for at least one year after the date of service, or longer if you are involved in an active dispute or appeal. For tax purposes, the IRS generally recommends keeping supporting documents for three to seven years after filing. If you have a chronic condition requiring ongoing treatment, retaining EOBs for the full course of treatment is advisable.

Why did I get an EOB for a free preventive visit?

Under the Affordable Care Act, most preventive services must be covered at no cost when performed by an in-network provider. However, you will still receive an EOB showing the billed amount and the plan’s payment. Your patient responsibility line should show $0. If it does not, the service may have been coded as diagnostic rather than preventive — a common error worth disputing.

What does “pending” mean on an EOB?

A pending status means the insurer has not finished processing the claim. This can happen when additional information is needed from the provider, when the claim requires clinical review, or during coordination of benefits with another insurer. Pending claims usually resolve within about 30 to 45 days.

Can I request an EOB for a past service?

Yes. Contact your insurer’s member services line or check their online portal. Most insurers retain claims data and EOBs for at least 18 to 24 months, and some keep records for several years. Medicare enrollees can view past claims in their Medicare.gov account.

What to Do Next

Make reviewing your EOBs a regular habit. Each time you receive one, spend two minutes comparing it to the service you received and any bill from the provider. Confirm the date, verify the service description, and check that your patient responsibility matches. If anything looks wrong, call your insurer before paying the provider’s bill. This simple practice catches duplicate charges, coding errors, and incorrectly processed claims — problems that collectively cost American patients enormous sums each year. Your EOB is not junk mail; it is your financial audit trail for every dollar your health plan spends on your behalf.

Sources

• Medicare.gov and the Centers for Medicare & Medicaid Services (CMS) — Medicare Summary Notice (MSN); how to read it; claims and appeals
• HealthCare.gov — how insurance works and Explanation of Benefits basics
• Internal Revenue Service (IRS) — Publication 502, Medical and Dental Expenses (7.5%-of-AGI threshold)
• American Medical Association (AMA) — claim processing and denial data