How to read your EOB.

If you've ever stared at an Explanation of Benefits (EOB) and felt like you needed a translator, you're not alone. EOBs are dense, full of insurance jargon, and the layout differs slightly between carriers. But once you know what the columns mean, the EOB becomes the single most powerful document for spotting billing errors — because it tells you, in your insurance company's own words, exactly what the hospital is allowed to charge you.

This guide breaks down every line on a typical EOB and shows you what to do with each number.

What an EOB actually is

An EOB is not a bill. The top of every EOB will say something like "This is not a bill" in bold somewhere. It's a statement from your insurance company describing how they processed a claim from a provider.

Specifically, the EOB tells you:

1. What the provider billed insurance for ("billed amount")
2. What insurance considers a reasonable rate for that service ("allowed amount" / "negotiated rate")
3. What insurance paid the provider
4. What you owe the provider

Number 4 is the magic number. It's the dollar amount your insurance has officially determined is your responsibility. If the provider later sends you a bill for more than this number, you have grounds to dispute it.

The eight columns you'll find on every EOB

Carriers use slightly different labels but the underlying data is the same across Aetna, BCBS, UnitedHealthcare, Cigna, Humana, Kaiser, and the rest.

1. Service date

The date of the procedure or visit. Important for matching the EOB to the corresponding line on your medical bill.

2. Service description / CPT code

What the provider claims they did. Example: "Office visit, established patient, 25 minutes" — CPT 99214. The five-digit CPT code is the standardized identifier. We'll come back to this in a moment.

3. Billed amount (sometimes "charges" or "submitted")

What the provider's billing system asked your insurance to pay. This is usually the provider's "chargemaster" rate — an arbitrarily high number that almost nobody actually pays. Hospitals routinely bill 3-10x the Medicare rate. Don't anchor on this number; it's not what's owed.

4. Allowed amount (sometimes "negotiated rate" or "contract rate")

This is the meaningful number. It's what your insurance has negotiated as a reasonable fee for that CPT code with that provider. If the provider is in-network, they signed a contract agreeing to accept this amount as payment in full (when combined with what insurance pays and what you owe).

If billed amount > allowed amount, that's normal. The "discount" or "adjustment" column will show the difference (sometimes called "PPO discount" or "negotiated discount"). The provider can NOT bill you for that difference if they're in-network. It's already a written-off charge by contract.

5. Plan paid (or "insurance paid")

How much of the allowed amount your insurance actually paid. Usually this is allowed amount - deductible - coinsurance - copay.

6. Deductible applied

If you haven't met your annual deductible yet, this column shows how much of the allowed amount was applied toward it. You owe this portion.

7. Coinsurance / copay

Your share of the allowed amount as a percentage (coinsurance) or a flat fee (copay). For example, 20% coinsurance on a $500 allowed amount = $100 patient share.

8. Patient responsibility (or "amount you owe")

The total of deductible + coinsurance + copay + any non-covered charges your insurance determined you owe.

This is the number that should match the bill the provider sends you. If the provider's bill is higher, something is wrong.

Comparing the EOB to your bill, line by line

Take both documents out. For each line on the bill:

1. Find the same CPT code on the EOB. Match by date of service AND code.
2. Compare the bill's "amount due" to the EOB's "patient responsibility" for that line.
3. If the bill is asking for more than the EOB says you owe, that's a potential balance-billing error.

Common mismatches:

• The provider bills you the full "billed amount" instead of the "allowed amount" — they're ignoring their contract with your insurance. Illegal if in-network. You owe only patient responsibility.
• The provider bills you a CPT code that doesn't appear on the EOB. They submitted the claim but insurance denied or didn't process it. You should call insurance to find out why, not pay yet.
• The provider's date is "March 14" but the EOB shows "March 14-15." Usually fine — multi-day visits combine. Sometimes a sign of double-billing.
• The provider bills the same CPT code twice on the same date, but the EOB only shows it once. Could be a legitimate two-procedure day OR a duplicate. Ask for documentation.

The "patient responsibility = $0" case

Sometimes you'll see EOB line items where patient responsibility is exactly $0. This means either:

• You've already met your annual out-of-pocket maximum, and insurance covers 100% from here
• The service was 100% covered preventive care (annual physicals, certain screenings, vaccinations are covered at 100% under the ACA)
• The provider was in-network and the claim was paid in full

If patient responsibility is $0 but you still get a bill — don't pay. Call the provider and your insurer. Most likely the provider's billing system didn't apply the contract correctly, or they're trying to balance-bill you. The EOB is your evidence.

"Pending" or "more information needed"

If part of the EOB is marked "pending" or "more information needed" or "denied," the claim isn't finalized. Don't pay the provider's bill until the EOB shows a final determination — otherwise you may overpay and have to fight to get the refund back.

A trick they don't want you to know

Every EOB has a phone number on it — usually the back, in small print — for member services. Call that number any time you have a question about a charge. The agents are paid by your insurance company, not the provider, and they can tell you:

• Whether the provider has been paid correctly
• Whether the charge you're being asked to pay matches what insurance said you owe
• Whether the provider was in-network on the date of service
• Whether the No Surprises Act applies to the situation

Don't wait until you've paid. Call first.

How Audra uses your EOB

When you upload a medical bill to Audra, one of the first things our auditor does is compare it line-by-line against your EOB (if available) and the federal/state billing rules. If the bill is asking for more than the EOB says you owe — by a single dollar or a thousand — we flag it as balance billing and draft the appeal letter for you.

Your first audit is free. If you have an EOB and a confusing bill, run them through and see what doesn't add up.