National Stock Exchange to revise pre-open auction framework from Sept 7

The move brings the pre-open process in line with the Closing Auction Session framework, creating a more consistent auction structure around price discovery at the start and close of the trading day

The National Stock Exchange (NSE) on Thursday announced it will introduce revised rules for its pre-open auction session effective September 7, 2026, in a bid to align the process with its Closing Auction Session (CAS).

 

In a post on X, the NSE said the overall duration of the pre-open session will remain unchanged at 15 minutes, from 9:00 a.m. to 9:15 a.m. However, the exchange will divide the session into separate stages for order entry, matching, and transition to continuous trading.

 

Under the new schedule, investors will be able to place both market and limit orders between 9:00 a.m. and 9:05 a.m. From 9:05 a.m. to 9:10 a.m., the exchange will accept only limit orders. This phase will have a random closure during the final two minutes.

 

 

Order matching will take place from 9:10 a.m. to 9:12 a.m. The following three minutes, until 9:15 a.m., will be used to move orders from the pre-open session to the Continuous Trading Session (CTS).

 

The revised mechanism also sets out the order in which trades will be executed. Market orders matched against other market orders will get the highest priority, based on time priority.

 

Any residual market orders will then be matched with limit orders using price-time priority. In the final stage, the remaining limit orders will be matched against limit orders, also on a price-time priority basis.

 

The move brings the pre-open process in line with the CAS framework, creating a more consistent auction structure around price discovery at the start and close of the trading day.

 

Revised pre-open session from September 7

 

Market and limit order entry: 9:00 am-9:05 am

Limit-order entry only, with random close in last two minutes: 9:05 am-9:10 am

Order matching: 9:10 am-9:12 am

Transition to continuous trading: 9:12 am-9:15 am

 

Alignment of Pre-Open Auction Session with the Closing Auction Session (CAS), effective September 07, 2026.#NSEIndia#NSE#CAS#PreOpenAuctionSession#CapitalMarkets#MarketStructure#Trading@ashishchauhanpic.twitter.com/6w97uDdC0i

— NSE India (@NSEIndia) September 3, 2026