Indian stock market: An important change from Dec 8 in pre-open session that you can't afford to miss out

Starting from Monday, December 8, the market will witness a pre-open session for equity derivatives (F&O) segment. The pre-open session will apply to both individual stock futures and index futures in the equity derivatives segment.

According to NSE, this session will run through a call auction process for 15 minutes, from 9:00 am to 9:15 am.

Three components of 15-minute session

Order entry period

9:00 AM – 9:08 AM: Traders can submit, change, or cancel orders. The system will apply a randomly timed closure between the 7th and 8th minute. The random closure for the equity pre-open and equity derivatives pre-open will occur separately.

Order matching and trade confirmation

9:08 AM – 9:12 AM: Once the order entry phase ends, the order matching window begins. During this time, the system calculates the opening price based on the equilibrium price and executes matching orders.

Buffer period

9:12 AM – 9:15 AM: This interval serves as a buffer, shifting the market from the pre-open phase into the regular continuous trading session.

Eligible contracts and trading session

The pre-open session is split into two phases — the Order Collection Period and the Order Matching Period.

In the Order Collection Period, traders can place, change, or cancel orders. Both limit and market orders are permitted, but special types such as stop-loss and IOC orders are not. Participants can also view real-time indicative prices, equilibrium calculations, and demand–supply data.

During the Order Matching Period, the exchange determines a single equilibrium price, which becomes the market’s opening price. Orders are matched in a fixed order: limit orders with other limit orders, remaining limit orders with market orders, and finally market orders with each other. No order or trade changes or cancellations are allowed at this stage.

All pre-open orders are checked for adequate margin before they are accepted. If a member doesn’t have enough capital to meet the margin requirement, the order will be rejected for the pre-open session, NSE added.

Disclaimer: This story is for educational purposes only. Please consult with an investment advisor before making any investment decisions.