Vat disclosure

Hi all,
XYZ company is following the practice of showing sales net of VAT till date.
but now it wants to show this item on gross basis and thereafter reduce VAT amount and show accordingly.
My question is  1. Can the company make such cangeover and if yes under what rule/section/legislation.
2. what are the disclosure requirements
3. also many companies show the sales on a gross basis and reduce excise duty. this is required under which legislation.
Kindly reply on urgent basis