Comment on BTST/ATST( Buy/Acquire Today Sell tomorrow)
No, the Exchange guarantees settlement which means that you either get shares or money back. On T+3, if the Exchange isn’t able to buy shares from the Auction market, then the close out (fund given in lieu of shares) is typically 20% higher than the price the stock is trading at.
Quoting this from the NSE website:
Closing out in the case of failure to give delivery for Normal Market
Close out will be at the highest price prevailing in the NSE from the day of trading till the auction day or 20% above the official closing price on the auction day, whichever is higher.