How to fight backBillSherpa · Updated 2026

How to Read Your Explanation of Benefits — What Every Line Means

Your Explanation of Benefits (EOB) is not a bill. It's the record of what your insurance company was charged, what they paid, and what they say you owe. It's also the most important document in any billing dispute — because the gap between what the hospital billed and what your insurer paid is where most errors hide.

What an EOB is — and what it isn't

Your EOB is a statement from your health insurance company explaining how a claim was processed. It comes after your insurer receives a claim from a provider and processes it. It is not a bill. It is your insurer's account of the transaction — and it's binding in the sense that what it says you owe is what you legally owe under your plan, not what the hospital's bill says.

The key columns on every EOB

Billed amount (or "charged amount")

This is what the hospital asked your insurer to pay. It's usually an inflated "chargemaster" rate — the hospital's list price, which exists for negotiation purposes and bears no relationship to the actual cost of care or to what you'll actually pay. Ignore this number for the purposes of figuring out what you owe.

Allowed amount (or "negotiated rate" or "approved amount")

This is the rate your insurer has negotiated with the provider. It's usually far lower than the billed amount. This is the number everything else is calculated from. Your deductible, coinsurance, and copay are all percentages of the allowed amount — not the billed amount.

Plan paid

The dollar amount your insurance company actually paid the provider, after applying your deductible and cost-sharing. This goes directly from your insurer to the hospital.

Your responsibility (or "amount you owe" or "patient responsibility")

This is what you legally owe under your insurance plan. It consists of some combination of your deductible (if not yet met), coinsurance (your percentage of the allowed amount), and copay (fixed amounts). This is the number you compare against the hospital's bill.

Adjustment / write-off

The difference between the billed amount and the allowed amount. The hospital has contractually agreed to "write off" this amount when they participate in your insurer's network. They cannot bill you for it — doing so is called balance billing and is often illegal.

How to use your EOB to spot billing errors

1. Get both documents side by side. Your EOB from your insurer and your itemized bill from the hospital. You need both.
2. Compare the procedure codes. Every service on your hospital bill should appear on your EOB. If something is on your hospital bill but not on your EOB, the insurer may not have processed it — or it may have been billed after you.
3. Compare the dates of service. Every line should show the same date. If the EOB shows a different date than your hospital bill for the same service, that's a discrepancy worth investigating.
4. Check "your responsibility" against what the hospital is billing you. The hospital can only bill you for the amount shown in the "patient responsibility" column of your EOB, plus any amounts your insurer denied for valid reasons. If the hospital's invoice exceeds the EOB patient responsibility, the excess is likely an error or illegal balance bill.
5. Look for denied claims. Your EOB will show if any services were denied. Note the denial reason code — these tell you whether the denial was due to a billing error (often fixable) or a coverage issue (requires a different process).

Common EOB problems and what they mean

"Denial — not medically necessary"

Your insurer determined the service wasn't required for your condition. This is appealable. Ask your doctor for a letter of medical necessity and file an internal appeal. More than half of medically necessary denials that are appealed get reversed.

"Denial — prior authorization required"

The provider didn't get advance approval from your insurer. If this was an emergency, it should be covered regardless. If it wasn't, ask your provider whether they obtained authorization and request the authorization records.

"Out of network — patient responsible for full balance"

Check whether the No Surprises Act applies. If this was emergency care or an out-of-network provider at an in-network facility who treated you without your advance consent, you should not owe more than your in-network cost-sharing 42 U.S.C. § 300gg-111.