ebTax where AP Bill To and AR Bill From taken from ?

Hi ,

  I am not quite clearly where the Bill To taken from in AP  and Bill From taken from in AR ?

In the Note:1595085.1 , it say in AP the Bill To Use the location of the Inventory Organization in Supplier - Purchasing tab in Financial Options window(N) AP Responsibility > Setup > Options > Financials Options). In AR the Bill From Use legal entity/operating unit address when creating transactions.

From the notes it means in AP the Bill To will look into OU's validation org.  In AR it both can use Legal entity and OU.

But I have one AP invoice, which didn't calculate tax ,because of the supplier associate legal entity didn't assign to the tax regime. After i assign the legal entity to the tax regime, then the invoice able to calculate the tax amount.  So i am confused.