Two documents show up after a hospital visit, and they look similar enough that most people file both and pay whatever the larger one says. That is exactly backwards. One of them is the insurer's math, and it is the tool that tells you whether the other one is honest.
What each document is
The bill (or statement) comes from the hospital. It is a demand for payment. The itemized version lists every charge; the summary version shows only a total.
The Explanation of Benefits (EOB) comes from your insurance company. It is not a bill - it usually says so, in small print, at the top. It is a record of a claim: what the provider charged, what your plan decided to allow, what the plan paid, and what portion is left for you.
The line that matters most on the EOB is your patient responsibility: the amount the insurer says you actually owe after its adjustment. That number is your anchor.
The columns on an EOB
A typical EOB row has these fields:
- Billed - what the provider charged (the same list price you see on the bill).
- Allowed - the most your plan will recognize for that service under its contract with the provider.
- Plan paid - what the insurer actually sent the provider.
- Adjustment - the difference between billed and allowed that the provider agreed to write off. This often carries a code such as
CO-45. - You may owe - your share (deductible, copay, or coinsurance) for that line.
That adjustment column is doing quiet, important work: it is money the provider is contractually not allowed to collect from you. For a fuller decoder of those codes, see what "CO-45" and other EOB codes actually mean.
The comparison that catches overcharges
Here is the whole trick. Put the itemized bill next to the EOB and compare two numbers:
- The "amount due from patient" on the hospital statement.
- The total patient responsibility on the EOB.
They should match. When the statement asks for more than the EOB says you owe, the gap is the problem. On a synthetic example I use throughout these guides, the hospital statement demanded $1,200.00 while the EOB put patient responsibility at $456.80. That $743.20 difference is not automatically yours to pay - it can be balance billing, a charge the insurer already adjusted away, or a statement the hospital sent before your insurance finished processing.
If the numbers do not match, do not pay the larger one. Call the billing department, say the EOB shows a patient responsibility of the smaller figure, and ask them to reconcile the statement to it.
What to do next
- Find the "you owe" total on your EOB.
- Find the "amount due" on your itemized bill.
- If the bill is higher, that gap is your first question - in writing, by phone, or both.
- If you do not have the itemized bill yet, request it. To read it once it arrives, use how to read an itemized hospital bill line by line, and to send the request, use the free letter tool.
An EOB feels like junk mail. It is actually the receipt that proves what you owe. Keep it, and compare it before you pay a cent.