Market pre-open rules change from today: Here's what is different

The new pre-open auction session from Monday is divided into three time slots for order entry, modification/cancellation and order matching/execution for determining the opening (equilibrium) price.

The National Stock Exchange (NSE) will implement the new pre-open auction session to help determine the opening prices for stocks. The new pre-open session is applicable for all stocks in equity cash market - including SME, InvITs/REITs and the derivatives segment. The overall market timing for the new pre-open session remains the same - i.e. from 09:00 am to 09:15 am. However, there are certain changes in the order entry, type of order entry, modifications, cancellations and matching/execution procedure when compared the earlier pre-open system in place till Friday, September 04, 2026. "The key objective of the revised pre-open session is to make opening price discovery more structured and efficient, while reducing the scope for last-minute market-order activity," says Sudeep Shah, Head- Technical and Derivatives Research at SBI Securities. Here's a step-by-step guide on the new pre-open session, and how it is different from the earlier pre-open session. Time slot 1: Order entry period New: According to a NSE circular, in the new pre-open session the order entry period will be from 09:00 am - 09:05 am. During this period, market participants can place both limit or market orders, modify and cancel them. 

 

 

 Old: In the older version, the order entry period was from 09:00 am - 09:08 am. You could place, modify or cancel orders during this period. The analyst from SBI Securities reckons that for traders, the first five minutes become more important, particularly during sharp overnight gaps or major news events. Time slot 2: Limit orders entry/ modification period New: From 09:05 am - 09:10 am, the exchanges will allow fresh entry of limit orders, and also modifications and cancellations of earlier placed limit orders. However, modifications or cancellations of market orders will not be allowed during this time window. The system may randomly close/ stop in the last two minutes of the set time-frame. Watch video: NSE pre-open session new rules explained Old: The time window was 09:00 am - 09:08 am for all such activities. Time slot 3: Order matching, trade confirmation period New: The order matching, and trade confirmation period starts from 09:10 am till 09:12 am, accordingly the opening price for the particular stock will be determined. Firstly, buy side market orders will be matched against sell side market orders in the order of time priority at the equilibrium price. The balance eligible market orders will be then matched with the limit orders placed as per price-to-time priority. And lastly, the remaining limit orders will be matched with limit orders in the order of price-time priority. Meaning, orders placed first closer to the matching price gets preference. No order entry, modification or cancellation will be allowed during this period. Old: The order matching and confirmation period was from 09:08 am till 09:12 am. Nandish Shah, Senior Derivative and Technical Analyst at HDFC Securities highlights that the key focus area of the new NSE pre-open is on change in order entry timing, and order matching with preference given to time and price priority. Time slot 4: Buffer period The buffer period remains the same in the new pre-open session, i.e. from 09:12 am - 9:15 am for transition from pre-open to continuous trading session. Here's how the opening price will be discovered: The opening price will be determined based on the principle of demand supply mechanism, also know as the equilibrium price. The equilibrium price is the price at which the maximum volume is executable. In case more than one price meets the said criteria, the equilibrium price will be the price at which there is minimum order imbalance quantity. Again in case of multiple such scenarios, the equilibrium price will be the price closest to the previous day's closing price.