Effective from August 3, 2026
Introduction
The Indian stock market is undergoing one of its biggest changes in recent years with the introduction of the Closing Auction Session (CAS) for equity markets.
The new framework changes how the closing price of eligible stocks is determined, extends the F&O market by 10 minutes, and introduces new trading timelines.
At Flattrade, we’ve updated our RMS and square-off timings to align with these changes.
What is the Closing Auction Session (CAS)?
The Closing Auction Session (CAS) is a dedicated auction conducted at the end of the trading day to determine the official closing price of eligible stocks.
Instead of using the VWAP of the last 30 minutes, the closing price is discovered through an equilibrium auction.
Initially this applies only to F&O stocks; other stocks continue with the existing VWAP methodology.
Why did SEBI introduce Closing Auction Session?
CAS improves price discovery, transparency, execution quality for institutional investors, derivative settlement, index calculation, mutual fund NAV accuracy and reduces tracking error.
Which Stocks are Covered?
| Stock Category | Closing Price Method |
|---|---|
| F&O Stocks | Closing Auction Session (CAS) |
| Non-F&O Stocks | Existing VWAP Method |
New Closing Auction Timeline
| Session | Time | Activity |
|---|---|---|
| Regular Equity Trading | 9:15 AM – 3:15 PM | Normal trading |
| Transition | 3:15–3:20 PM | Reference price calculation |
| CAS Order Entry | 3:20–3:25 PM | Market & Limit Orders |
| Final Order Entry | 3:25–3:30 PM | Limit orders only; random close |
| Order Matching | 3:30–3:35 PM | Closing price discovery |
| Post Close | 3:50–4:00 PM | Execution at closing price |
How is the Closing Price Calculated?
The closing price is determined using an Equilibrium Price Mechanism.
Simply put:
- All buy and sell orders are collected.
- The system identifies the price where the maximum quantity can be matched.
- If multiple prices satisfy this condition, additional rules are applied to select the final equilibrium price.
This method is considered more robust than using the last 30 minutes’ VWAP.
Orders Allowed During CAS
Allowed
- Market Orders
- Limit Orders
Not Allowed
- Stop Loss Orders
- Iceberg Orders
Unexecuted limit orders from the regular market will automatically carry forward into CAS if they fall within the applicable price band.
Pre-Open Session Changes (Effective September 7, 2026)SEBI has also aligned the Pre-Open Auction Session with the CAS framework.
| Session | Old | New |
|---|---|---|
| Order Entry | Existing | Market & Limit Orders |
| Second Phase | Existing | Limit Orders Only |
| Random Close | No | Yes (9:08–9:10 AM) |
| Matching | Existing | Equilibrium Price |
| Information | Limited | Indicative price, quantities & imbalance |
New Market Timings
| Segment | Current | New |
|---|---|---|
| Equity (F&O Stocks) | 9:15–3:30 | 9:15–3:15 |
| Equity (Other Stocks) | 9:15–3:30 | No Change |
| F&O | 9:15–3:30 | 9:15–3:40 |
Flattrade RMS Policy Changes
| Policy | Current | New |
|---|---|---|
| Equity Intraday Auto Square-off | 3:15 PM | 3:00 PM |
| F&O Intraday Auto Square-off | 3:15 PM | 3:25 PM |
| Equity Trading (F&O Stocks) | Till 3:30 PM | Till 3:15 PM |
| Equity Trading (Other Stocks) | Till 3:30 PM | No Change |
| F&O Trading | Till 3:30 PM | Till 3:40 PM |
What Changes for Flattrade Customers?
To align with the new exchange timings and ensure smooth risk management, Flattrade is updating its RMS policy.
Intraday Square-off Timings
| Segment | Current RMS | New RMS (From Aug 3) |
|---|---|---|
| Equity Intraday | 3:15 PM | 3:00 PM |
| F&O Intraday | 3:15 PM | 3:25 PM |
Market Closing Timings
| Segment | Current | New |
|---|---|---|
| Equity (F&O Stocks) | 3:30 PM | 3:15 PM |
| Equity (Other Stocks) | 3:30 PM | 3:30 PM (No Change) |
| F&O | 3:30 PM | 3:40 PM |
Key Dates
| Date | Change |
|---|---|
| August 3, 2026 | CAS implementation, new timings & RMS changes |
| September 7, 2026 | Pre-open framework changes |
The introduction of the Closing Auction Session marks a significant step in modernising India’s equity markets.
By adopting a globally accepted auction-based closing price mechanism, SEBI aims to enhance transparency, improve price discovery, and provide a more efficient market close for all participants.
