For intraday: For now, there will be no change because currently, exposure allowed is less than 20X. For Delivery sell: Effective December 1st we will only be able to release 80% of the sell value for that day. It means if you sell stock worth Rs.1,00,000. Then only 80,000 will be released as a margin which can be used to purchase any other stock. From the next day i.e. T+1, 100% sell value will be available for trading. Buying back delivery sells on the same day: If you sell stocks, we will release an 80% margin under the presumption that we will be able to deliver these shares to exchange in early pay-in.  

(a) If you don't take any further position on such margin release against sale there will be no change and you can buy these shares back. 

(b) However, if you take further positions in other stocks and either carry such position or square it off later during the day and also buy the original shares sold against which margin was released then, it will attract a margin penalty because there will be no sell obligation and we will not be able to do early pay-in to exchange.