What's the use of the tax1, tax2 and tax3 columns

[Guido1982]

Thanks, I knew that, but let me explain myself better:

When I set (for instance) a sales order to 'individual', only the first TAX rule appears in the inventoryline, even though I've activated three. When I set the SO to 'group', I can fill out the three tax type individually. I tried this in the demo as well. My point is, why are three tax types saved for each inventoryline, while you can only use them for an entire record (in this case a sales order)?