How to check a medical bill against your EOB: a worked example with deductible, coinsurance and out-of-pocket max

A bill from a doctor or a lab is a request for money, not a statement of what you owe. What you owe comes from your plan's rules, applied to each claim in the order your insurer processed it. Here is one year of claims, worked through with the sample file of our deductible and out-of-pocket tracker. Every figure comes from the same model, which was checked claim by claim. The plan and the claims are examples: use your own numbers from your Explanation of Benefits (EOB).

The plan

The rules, as on most plans: on a claim that goes toward the deductible, you pay the plan's allowed amount until the deductible is met, then 20% of the rest. A copay counts toward the out-of-pocket maximum but not the deductible. Preventive care is covered in full. Once you've paid the out-of-pocket maximum, covered in-network care costs nothing more that year. Some plans differ, for example copays that only start after the deductible, so check yours.

Seven claims, in date order

The copays go toward the out-of-pocket maximum only, so after the specialist visit the deductible still has $1,800 to go. The surgery uses it up: $1,800 toward the deductible, then 20% of the remaining $8,000, which is $1,600. From then on every claim is 20%.

The lab bill is the one that doesn't match. It asks for the full $310 allowed amount, as if the deductible were still open, but by the time the lab claim was processed the deductible had been met, so you owe 20%: $62, not $310. That is $248 overbilled. The plan paid $7,968 of the $12,900 allowed.

Why the order of claims matters

Suppose the same lab work had been the first claim of the year. Then it would sit entirely inside the deductible, and $310 would be the right bill. The surgery would then carry only $1,490 of deductible plus $1,662 of coinsurance, $3,152 in all, so a surgery bill of $3,400 would be the one $248 too high. The total for the year is $4,932 either way. What changes is which bill carries the deductible, which is why each bill has to be checked against the claims that came before it, in the order the insurer processed them, not just against the year's total.

At the out-of-pocket maximum

After these seven claims, $4,932 has gone toward the $7,500 out-of-pocket maximum, so $2,568 is left. At 20% coinsurance, that is $12,840 more of allowed charges on deductible-type claims before the plan pays everything.

Say a second surgery follows with $15,000 allowed. 20% would be $3,000, but you only owe the $2,568 left to the maximum. After that, a specialist visit with a $40 copay costs $0: a $40 copay collected at the desk is money to ask back.

How to check your own bills

1. Get the EOB for each claim from your insurer's website. Use the allowed amount, not the provider's charge: an in-network provider has agreed to accept the allowed amount, so the difference isn't yours to pay.
2. Put the claims in the order the insurer processed them and track how much of the deductible and out-of-pocket maximum each one uses.
3. Compare each bill with what you should owe. The EOB's "patient responsibility" line should agree with your figure. If a bill arrived before the EOB, wait for the EOB before paying.
4. If a bill is higher, call the provider's billing office with the EOB in hand. If the EOB itself looks wrong, call the insurer.

The free medical bill calculator does this for a handful of claims, pre-filled with this example. The spreadsheet tracks up to 200 claims for the year, flags each bill that doesn't match, and keeps a running total of what you have paid and what's still to pay.