If you sell stocks from your Demat or T1 (BTST), only 80% credit against the sale amount will be available for further trades in the same/other segments on the selling day, according to SEBI's new peak margin requirements. The remaining 20% credit will be held in Trading portals's "delivery margin" field until the next trading day.

The following table summarizes the key changes that occurred as a result of the implementation of the upfront and peak margin norms:
Action Before implementation of the peak & upfront margin rules From 1st December
Stocks sold from Demat holdings Proceeds can be used to purchase further equities or to engage in F&O trading. 80% of the proceeds can be used to buy equities or trade F&O. The remaining 20% will be accessible for trading the next trading day..

Stocks sold from T1 holdings (i.e. BTST) Proceeds can be used to purchase further equities or to engage in F&O trading. You can buy other stocks with 80% of the proceeds and trade in F&O with 60% of the proceeds.

Intraday profits earned
On the same day, proceeds can be used to buy stocks or trade F&O.
Earnings cannot be used until the exchanges have settled, i.e. T+1 for F&O and T+2 for Equity.
Options sold On the same day, you can use the proceeds to buy stocks and trade in either currency or equities F&O.
Option sale credit for stock options can only be used to buy options in the same segment; for example, option sell credit for stock options cannot be used to buy currency options.
Hedged Position
When the trade with additional risk/margin isn't carried overnight, you can quit any leg first without incurring a margin penalty, even if there is an intraday margin deficiency.
If appropriate margins are not available, exit the higher risk/margin position first, as margin requirements will be reviewed intraday, and deficits may result in a penalty.