What is an EOB, and why does it say I owe money?

A: An explanation of benefits is your plan's receipt for a claim, and the first thing to know is that it is not a bill. It shows what your therapist charged, what your plan decided the service is worth, what the plan paid, and what it thinks is left for you. Four numbers do all the work: the billed amount (what your therapist asked for), the allowed amount (what your plan says the service is worth — usually less), the plan paid, and your responsibility. Your share is calculated against the allowed amount, not the billed one, which is why the maths often looks wrong at first glance.

Worked example: therapist bills $200. Plan's allowed amount is $140. You have a $40 copay, so the plan pays $100 and your responsibility is $40. Your therapist writes off the $60 difference because they are in-network and agreed to. Out of network, that $60 does not disappear — and that is the whole reason the superbill maths surprises people.

Three things to check every time. Does the number of sessions match what you actually attended? Is the code the one your therapist said they would bill? And has your deductible been applied — early in a plan year "your responsibility" can be the full allowed amount until the deductible is met, which is not an error.

Do this: if the EOB and your therapist's bill disagree, call the plan first with the claim number from the EOB, and get a reference number for the call. Errors at this stage are usually coding or eligibility mismatches and get fixed on the phone. If the plan denied the session rather than repriced it, that is an appeal, and it is free. How to appeal a denial →

Sources: CMS explains each EOB field and confirms that an EOB is not a bill: How to read an explanation of benefits. See also allowed amount and copay vs coinsurance.

Keep EOBs for the deduction: Can I deduct therapy on my taxes? →