How to read your Explanation of Benefits (EOB)

A few weeks after a medical visit, a document shows up from your insurer titled "Explanation of Benefits," usually with "THIS IS NOT A BILL" printed somewhere on it. The numbers don't match what you expected, so most people file it straight in the recycling. Don't. The EOB is how you catch billing errors before they turn into charges you actually pay.

What an EOB actually is

It's your insurer's summary of a claim: what the provider charged, what your plan agreed to pay, what got knocked off, and what portion is yours. It isn't a bill — that comes separately from the provider — but it tells you what that bill should say. Think of it as the answer key you check the bill against.

The numbers that matter

Most of an EOB is noise. A few lines do the real work:

• Billed amount — the provider's sticker price. Almost no one pays this.
• Allowed amount — the discounted rate your insurer actually recognizes. This is the number that matters.
• Plan paid — what your insurer covered.
• Your responsibility — what you owe after copay, deductible, and coinsurance. This is what the real bill should match.

How to use it

When the provider's bill arrives, compare it to the "your responsibility" line on the EOB. They should agree. If the bill is higher, call the provider's billing office — sometimes it's just timing, sometimes it's an error worth disputing. While you're at it, scan for services you don't remember getting, or an "out-of-network" flag on a provider you thought was in-network. Both are common, and both are worth a phone call.

If something's off

Start with whoever made the mistake. A coding error is usually the provider's billing office; a coverage question — why wasn't this covered? — is your insurer. Get a name, date, and reference number for every call. Billing errors are common, and the people who catch them are the ones who actually read the EOB.