India's equity markets are set for one of their biggest operational changes in recent years. From August 3, 2026, the Securities and Exchange Board of India (SEBI) and the National Stock Exchange (NSE) will introduce the Closing Auction Session (CAS) for eligible Futures & Options (F&O) stocks, fundamentally changing how closing prices are determined.
The introduction of the Closing Auction Session marks a significant structural change in India's equity markets. While long-term investors may notice little difference in day-to-day investing, the new framework is expected to have a much bigger impact on F&O traders, brokers, institutional investors and passive funds,
The new framework not only replaces the existing Volume Weighted Average Price (VWAP)-based closing mechanism for F&O stocks with an auction-based system but also extends equity derivatives trading by 10 minutes, creating different closing times for different segments of the market.
Here's everything investors need to know.
1. Three different market closing times will now apply
The biggest change is that the market will no longer have a single closing time.
Non-F&O stocks Normal trading till 3:30 PM (No change)
F&O stocks (cash market) Continuous trading till 3:15 PM, followed by CAS till 3:35 PM
Stock & Index F&O Trading till 3:40 PM
Post-close session 3:50 PM – 4:00 PM
This means investors trading different market segments will need to follow different closing schedules.
2. Equity derivatives will trade for 10 extra minutes
The NSE has extended trading hours for equity derivatives from 3:30 PM to 3:40 PM.
The additional 10 minutes are intended to align derivatives trading with the new auction-based closing process in the cash market.
3. F&O stocks will no longer close like other shares
For stocks that are part of the F&O segment, normal trading will end at 3:15 PM.
Instead of trading continuously until 3:30 PM, these stocks will move into the Closing Auction Session, where orders are collected and matched to determine a single closing price.
Regular cash market trading remains unchanged for stocks that are not part of the F&O segment.
4. Here's how the Closing Auction Session will work
The new auction process will follow a structured timeline:
Time Activity
3:15 PM – 3:20 PM Transition from Continuous Trading Session (CTS) to CAS and reference price calculation
3:20 PM – 3:25 PM Market and limit orders can be placed
3:25 PM – 3:30 PM Only limit orders allowed; market orders cannot be modified or cancelled
3:28 PM – 3:30 PM Random order-entry closure
3:30 PM – 3:35 PM Order matching and closing price discovery
5. The closing price calculation is changing
Currently, the closing price is determined using the Volume Weighted Average Price (VWAP) of trades executed during the final part of the trading session.
With the rollout of CAS, all buy and sell orders will instead be pooled together and matched at a single equilibrium price, which will become the official closing price for eligible F&O stocks.
According to SEBI, this approach is expected to improve price discovery by reflecting the combined demand and supply from all market participants, rather than prices from trades executed at different times.
6. The VWAP calculation window is also changing
The VWAP window used for derivatives will now run from:
3:10 PM to 3:40 PM
instead of the earlier last 30-minute calculation ending at 3:30 PM.
7. What changes for F&O traders?
The extended trading session gives derivatives traders additional time to:
Hedge open positions
Adjust trades after the cash market auction
Exit intraday positions
Manage expiry-day volatility
React to auction-based closing prices
8. Why are regulators introducing CAS?
According to SEBI, the new mechanism is aimed at improving the efficiency of closing price discovery.
By collecting all buy and sell orders into a single auction pool, the regulator expects the closing price to better represent actual market demand and supply.
9. Nithin Kamath explains why the change matters
Zerodha co-founder Nithin Kamath said the new mechanism could improve price discovery and make execution of large trades more efficient.
He explained that passive funds tracking benchmark indices often execute large trades near the market close to match index levels, and those transactions can move stock prices while being executed, increasing tracking error. According to Kamath, the Closing Auction Session can significantly reduce this problem for index funds and exchange-traded funds.
Kamath also noted that large trades placed in the final minutes of trading can disproportionately influence the closing prices of stocks and indices. Since CAS aggregates all buy and sell orders before matching them at a single price, he said it becomes much harder to influence the market close.