Can I buy and sell shares across the two exchanges?

Yes, you can purchase shares on one market and sell them on another the next day, i.e.,, T+1 day, rather than the same day. For example, if you buy 100 Infosys shares on the NSE on Monday, you can opt to sell 100 shares on the BSE on Tuesday.

As an illustration, consider the following:

Assume the stock of Reliance is trading at 2600 on the NSE and 2604 on the BSE. When the price difference is smaller than 4 (2604 - 2600), you can make an intraday arbitrage trade by purchasing on the NSE at 2600 and selling on the BSE at 2604. If the difference between the NSE and BSE prices is less than four, you earn; otherwise, you lose.

This is an arbitrage trade since it makes no difference whether Reliance rises or falls; only the price differential between Reliance on the NSE and the BSE counts.

If you already have equities in your demat account, you may presently conduct an arbitrage deal. So, if you held Reliance in your demat account, you could sell it at 2604 on the BSE and instantly purchase it at 2600 on the NSE, cutting your holding cost. You will not be able to place fresh intraday sell and purchase orders on various exchanges.

If you do not square off these spots by 3:20, they will be auto squared off. There are no charges for auto squares off the positions.

If you place an order for a stock which is listed on both markets, you may sell it on one and purchase it back on the other. Even if these trades are classified as CNC, all costs, including the STT, will apply to intraday transactions.