New stock market pre-open session rules starting today: What’s changing for you?

After making changes in the closing session methodology, the National Stock Exchange (NSE) is now set to revise its order entry rules for the pre-opening session of the stock market starting September 7. While the general 15-minute pre-open period will remain unchanged, the rules governing when traders can place markets and limit orders will change.The revised agreement makes the pre-opening process more similar to the auction mechanism followed during the Closing Auction Session (CAS). NSE said the objective is to bring the mechanism used to determine market opening closer to the framework already followed for the closing auction.The pre-opening session will continue to operate between 9:00 a.m. and 9:15 a.m. However, the order entry period from 9 a.m. to 9:10 a.m. will now be split into two five-minute windows.Between 9 am and 9:05 am, traders will be able to submit, modify or cancel both market and limit orders. Once this window ends, the rules will change. From 9:05 am to 9:10 am, NSE will only accept limit orders, which means any market order submitted during this five-minute period will be rejected.The review is particularly relevant for traders who tend to place orders towards the end of the pre-open session. Under the new agreement, a market order cannot be entered after 9:05 am. Therefore, traders who wish to place an order during the period from 9:05 am to 9:10 am will have to specify the price using a limit order.

How will the new pre-opening session work?

The first order entry window will be extended from 9 am to 9:05 am Investors will be able to enter new orders and modify or cancel existing orders during this period, with both market orders and limit orders allowed, according to an ET report.The second window will begin at 9:05 am and end at 9:10 am During these five minutes only limit orders can be entered. NSE has also stipulated that this phase may be closed randomly during its last two minutes.Once order entry is complete, the exchange will conduct order matching between 9:10 am and 9:12 am. This will be followed by a three-minute transition period from 9:12 am to 9:15 am, after which the regular market session will begin.There are no changes to the start of normal trading. The stock market will remain open at 9:15 a.m. The revision applies only to the rules governing order entry during the pre-open auction.

What changes for merchants?

A market order instructs the exchange to execute a buy or sell transaction at the best price available at that time. While these orders are easy to place, the actual price at which the trade is completed is not known in advance. This uncertainty can be more pronounced when the market opens with a significant gap or when a stock experiences high volatility.Limit orders offer greater control over the price. A buyer using this type of order specifies the highest price he or she is willing to pay, while a seller specifies the lowest price he or she is willing to accept.Under the revised system, traders entering orders between 9:05 am and 9:10 am will have to opt for limit orders. The change could help reduce the possibility of abrupt price distortions as a result of placing market orders at the end of the pre-open period.NSE has also specified the sequence in which orders will be matched under the revised pre-opening mechanism.Market orders that can coincide with other market orders will be given the first priority, and orders will be considered based on time priority. Once these trades are posted, any remaining market orders will be compared to limit orders based on price-time priority.The final cassation stage will involve the limit orders that are still pending. These will be compared to other limit orders using the same price-time priority mechanism.(Disclaimer: Recommendations and views on the stock market, or any other asset class or personal finance management tips provided by experts and analysts are their own. These views do not represent the views of The Times of India.)