You surely do not want a situation where you need to sign and submit a Debit Instruction Slip (DIS) physically each time you make a sell transaction. That is just too cumbersome. It creates a problem in terms of availability of DIS, maintaining your DIS in a safe and secure manner as well as avoiding problems of misuse of your DIS. These problems can be obviated through online demat facility which does away with physical intervention and makes the entire process straight and seamless.