VAT calculation with Purchase order or any inventory trans should no reflect to the Item Cost and no

Dear,

As per our scenario, while entering any PO , the system is also calculating the VAT/tax amount which I should not be included with item cost after the purchase receipt and systems should not create any GL entry for vat.

please advise, in order to achieve these criteria, what, cost element, cost component mapping set I can follow for VAT calculation which should not inculde reflect the item average cost.