Field help (POHVDTAVAT) 

This field indicates the tax code of the invoicing element.
Only one tax code consistent with the legislation and the group of the site company can be entered.
SEEREFERTTOThe general principles linked to the multi-legislation setup are detailed here.

An invoicing element with 'product rate' or 'line amounts' as tax calculation rule does not display a tax code and unauthorizes the modification of this tax code.