How to read an EOB (Explanation of Benefits)

An envelope arrives from your insurance company. Inside is a page of numbers — a large one, a smaller one, something called an adjustment — and printed across the top, usually in bold capitals: THIS IS NOT A BILL.

So what is it, and why did they mail it to you?

It’s an Explanation of Benefits, or EOB. It is your insurance company’s account of what happened after you got care: what the hospital asked for, what your plan agreed to count, what the plan paid, and what it expects to land on you. Nothing is due from this piece of paper.

Most people file it somewhere or throw it away. Read it instead. It takes about five minutes, and it is the most useful document you will get about that visit — because the bill that shows up later should agree with it.

The five numbers that matter

Insurers use different words for the same things, so look for the meaning rather than the exact label.

Amount billed. What the provider asked for. This number is often startling, and it is rarely what anyone actually pays. Hospitals keep a list price — the chargemaster — that mostly functions as an opening position.

Allowed amount (also “negotiated rate”, “eligible charges”, “plan discount rate”). The most your plan will count for that service under its contract with that provider. This is the number that actually drives everything below it.

Provider adjustment (also “discount” or “write-off”). The gap between what was billed and what’s allowed. If the provider is in your network, they agreed by contract to accept the allowed amount, so that gap simply disappears — they cannot bill you for it. A large adjustment is not a sign that something went wrong. It’s the arrangement working the way it was designed to.

Plan paid. What your insurer actually sent the provider.

Your responsibility (also “patient responsibility”, “amount you may owe”). Your deductible, copay, and coinsurance, plus anything the plan didn’t cover. Remember this number.

The one comparison worth making

Weeks later, the hospital or the doctor’s office sends an actual bill. Put the two documents side by side and check one thing: does the amount they’re asking for match the “your responsibility” figure on the EOB?

If it does, the system worked. Pay it — or, if you can’t, ask about a payment plan or the hospital’s financial assistance policy before the balance ages into collections.

If the bill is higher than the EOB says it should be, don’t pay it yet. Something needs explaining, and asking costs nothing.

That single comparison catches a large share of ordinary billing problems. It requires no expertise. It’s just two numbers.

Why the two don’t match

There are four common explanations, and only one of them is really your problem.

The bill was sent before insurance finished processing. Very common, and it resolves itself. Check the date on the bill against the date on the EOB. If the bill is older, wait for an updated statement.

The provider was out of network. Then the allowed-amount protection may not apply, and they may bill you for the difference. Two important exceptions: under the federal No Surprises Act, in effect since 2022, you generally can’t be balance-billed beyond your in-network cost sharing for emergency care, or for an out-of-network provider who treated you at an in-network facility (CMS). Many people are billed anyway and never learn they had grounds to question it.

Something was coded or entered wrong. A duplicate charge, a service you don’t recognize, a quantity that doesn’t look right. You can’t see any of this on a summary bill, which is why the next section matters.

The plan denied part of it. The EOB will carry a reason code — needs prior authorization, not medically necessary, out of benefit period. A denial is not the end of the conversation; you generally have the right to an internal appeal, and then to an independent external review by someone outside your insurance company (HealthCare.gov).

Ask for the itemized bill

What most hospitals send first is a summary — a few category lines and a total. The itemized bill is the real one: every service, every supply, with its billing code and price.

You are entitled to ask for it, and asking is routine. Billing departments handle the request every day.

When it arrives, read it against the EOB. You’re not looking for fraud. You’re looking for the ordinary things: a charge dated for a day you weren’t there, the same item twice, a supply you never received, a room rate for a night you went home.

If something looks wrong, you don’t need to prove it. You need to ask about it.

Questions, not accusations. The person on the phone did not create the bill, and they are far more useful to you as an ally.

If you can’t pay it

This rarely comes up on its own, so ask directly. Nonprofit hospitals are generally required by the IRS to establish a written financial assistance policy and to make it widely available, including on their website (IRS Section 501(r)(4)). It’s often called charity care, and eligibility frequently reaches further up the income scale than people assume.

You are not asking for a favor. You are asking a hospital for the policy it is already required to have.

And if a bill has already gone to a collection agency: that letter is not proof that you owe the money. Under federal debt collection law, if you dispute it in writing — generally within 30 days of receiving their validation notice — the collector must stop collection activity until they send you verification responding to your dispute (CFPB).

When the paperwork isn’t in a language you read

This is the part that doesn’t get written about much. Millions of families in the United States get medical paperwork in a language and a vocabulary nobody at the table knows, and they do the only safe-seeming thing available: they pay it.

That is why we built Mareva. You upload the bill, the EOB, or the denial letter, and it explains in plain language — in your language — what the document says, what the amounts mean, and what looks worth questioning. The basic scan is free, it reads ten languages, and the dispute letters it drafts stay in English, because that’s who they’re going to.

It won’t promise you a number. Nobody honest can. It makes sure you can read what you’re being asked to pay before you pay it.