The National Stock Exchange (NSE) will introduce the Closing Auction Session (CAS) in the equity cash segment from August 3, 2026. The exchange will also extend trading hours for the equity derivatives segment by 10 minutes, with trading continuing until 3:40 PM.
CAS is an auction-based mechanism that will be used to determine the closing price of eligible securities in the cash market.
What Is the Closing Auction Session?
The Closing Auction Session is a separate session conducted after regular trading for eligible securities. During this session, buy and sell orders are matched, and an equilibrium price is determined. This equilibrium price becomes the official closing price of the security.
Initially, CAS will apply only to securities in the cash segment that have derivative contracts available. NSE has stated that the framework may be extended to additional securities in phases.
When Will CAS Be Held?
The Closing Auction Session will take place after the end of regular trading in eligible securities.
The process includes:
- 3:15 PM to 3:20 PM: Reference price calculation and transition period.
- 3:20 PM to 3:25 PM: Order entry period for market and limit orders.
- 3:25 PM until a random closure between 3:28 PM and 3:30 PM: Limit order modification and cancellation period.
Order entry will not be permitted during the transition period from 3:15 PM to 3:20 PM.
What Changes for the F&O Segment?
NSE has extended trading hours in the equity derivatives segment from 3:30 PM to 3:40 PM.
The revised timing will apply to both stock and index derivatives contracts.
Which Securities Will Continue Under Existing Timings?
Non-F&O securities in the equity segment will continue to trade under the Continuous Trading Session (CTS) until 3:30 PM.
What Happens to Existing Orders?
Unexecuted limit orders from the Continuous Trading Session may be carried forward to CAS, subject to applicable rules.
However, certain order types, including stop-loss orders, disclosed quantity orders, iceberg orders, and orders outside the applicable CAS price band, will be cancelled by the exchange.
Implementation Timeline
The Closing Auction Session framework will be implemented from August 3, 2026.
NSE has separately stated that the alignment of the pre-open auction session framework with CAS is scheduled to take effect from September 7, 2026.
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