The National Stock Exchange (NSE) changed its pre-open session rules from September 7, 2026. The revised stock market rules change when traders can place market and limit orders. 

The NSE introduced the changes across the equity market to create a more structured opening auction. The 15-minute pre-open session still runs from 9 AM to 9:15 AM. The new system divides order entry into two five-minute phases before price discovery begins.

From 9 am to 9:05 am, traders can enter, modify, or cancel market and limit orders. From 9:05 am to 9:10 am, only limit orders can be entered, modified, or cancelled. NSE will reject market orders placed after the 9:05 am cut-off. 

The exchange will then match orders between 9:10 am and 9:12 am. Regular stock market trading will continue to start at 9:15 am. 

The revised pre-open rules bring the opening process closer to the Closing Auction Session mechanism. NSE aims to create a more consistent approach toward price discovery. The framework also separates order collection from actual order matching during the opening auction. 

The change carries particular importance for traders who frequently use market orders near the opening bell. Market orders will now have only five minutes during the pre-open session. Limit orders provide greater price control during the remaining order-entry window.

NSE will also give priority to market orders matched against other market orders. Remaining market orders will then match with limit orders using price-time priority. Pending limit orders will follow the same matching principle. 

The second phase can also close randomly during its final two minutes. Traders therefore face greater timing pressure when placing orders near the session's end. The revised system covers equity securities beyond major listed companies, including SME shares, REITs, and InvITs.

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