By Gurpreet 

The NSE and BSE introduced the concept of the pre-open session to reduce the volatility of securities and provide better price discovery in the markets. Pre-market sessions are conducted on a daily basis at the exchange. 

The pre-open market session lasts for 15 minutes from 9 AM to 9:15 AM and is divided into three parts:

1. Order Collection: In the first 8 minutes, orders are placed, modified or canceled. One can place only limit orders or market orders. The order collection window can close at any time between 9:07 AM and 9:08 AM. 
2. Order Matching: In the next 4 minutes, price discovery will be done, and orders will be executed. 
3. Buffer Period: The last 3 minutes are used to facilitate the transition from pre-open to regular session.

After the closure of the collection window to 9.15 AM new orders cannot be placed. The orders placed are matched and trades are confirmed.

One can place orders only in the cash segment. Stop Loss orders are not allowed. Finally, The orders that have not been traded are carried forward to the normal trading session. Detailing on such orders below:

1. Limit Orders that are not traded during Pre-Open Session will be moved to normal trading sessions at the same price.
2. Market Orders that are not traded during the Pre-Open session will be moved to the normal trading session at the Opening Price.