Promotional items and VAT in NAV 2015

Hey guys 

My company often give free goods for customers (Promotional goods) but yet company has to pay the VAT 15% tax for the government and on the promotion invoice we set the selling price to 0 and when you do that the VAT base also comas to 0 because there is no amount for the VAT to calculate on.SO is there a way for me to do little code manipulation from behind.Also i am not a developer but i can do little customization and i know the way around the dev. environment.


Thanks in advance