NSE and BSE implement new pre-open session rules

India’s major stock exchanges, the National Stock Exchange (NSE) and the BSE, have implemented new rules for the pre-open session effective September 7. While the total duration of the session remains 15 minutes (9:00 a.m. to 9:15 a.m.), the internal mechanism for order collection and price discovery has been restructured to mirror the closing auction process.

The new framework divides the session into specific phases. From 9:00 a.m. to 9:05 a.m., investors can place, change, or cancel both market and limit orders. Between 9:05 a.m. and 9:10 a.m., the window shifts to limit orders only; market orders are no longer permitted, and existing market orders cannot be modified or withdrawn. Order matching and the determination of the opening price will now occur between 9:10 a.m. and 9:12 a.m., followed by a buffer period before continuous trading begins at 9:15 a.m.

These changes apply to the equity cash market, including mainboard stocks, SME shares, InvITs, and REITs, as well as the derivatives segment.