Vces

Hi friends I need an information regarding VCES.. If a company fails to utilise the VCES option means what will be the position for company on payment of Service Tax? One of my friend said that company will be charged interest from the date of Service tax payable till date.Just assume company has not paid service Tax for 3 years from the year 2010, now if the company wants to pay interest now means, which rate will be applicable for them? whether interest rate pertaining to that particular years or interest rate applicable at present? Can u give your advice.. Thanks & regards Mukund