not agree with Harpreet singh .If a seller not charged vat , in this case it is assumed that in the total amount vat is included by the purchase, but at the time of assessement of sale tax it create problem, the sale tax authorities will cancel your input which u hve taken on purchase or either u hve to sign one form from the purchase in haryana C4 form is used.
In short Always ask to seller to whom you are purchasing good to show vat in invoice , means vat included bill is not advisable.