Correct math, wrong rule: when your plan is applied incorrectly

This Explanation of Benefits was arithmetically perfect. Every column added up. It was still wrong.

Divide the coinsurance by the amount it should have been calculated on and you get 40 percent. The plan prices that service at 20 percent. On one claim that is $264.

This is the second family of billing error: the page is internally consistent, but the wrong rule was applied. It is invisible if you only ever look at the EOB, because nothing on the EOB tells you what the rate should have been.

The four patterns that cover most of it:

• The rate is higher than your plan states.
• A flat copay was applied more times than the plan allows.
• A deductible was charged on a service your plan exempts.
• You were charged two kinds of cost sharing where the plan prices only one.

One thing worth knowing about the rate case. It is usually not a typo. Often the claim was priced in the wrong network tier, so check the tier before you argue about the percentage.

And a discipline that decides whether you win: only raise this when you can quote the sentence. Not your interpretation of the benefit, the actual line from the services table.

General information, not legal, medical or financial advice. Every plan is different, so check the details against your own plan documents.