thank you very much sir
i read something about T+2 and T+3 but i didnot understand much
Settlements are on T+2 basis. Once in while they will change the settlement day based on holidays, but T+2 is the usual pattern. That implies that if you short sell on Monday, you need to have shares in your account on Wednesday.
This gives you a window of opportunity to short sell on Monday and somehow get shares in your account by Tuesday to have a happy settlement. However, it is easier said than done. You can not buy on Tuesday as they will hit your account on Thursday after they settle. The thing which could happen is when you have either given a demat request and are waiting for it to hit your account, or you have given an offline transfer (from another account) and waiting for that to hit those account. There may be others, but only in those extreme circumstances will you be able to short sell today and meet the T+2 settlement requirements without going into auction.