SEBI and the exchanges have replaced the way the official closing price of a stock is determined. Until now the close was a volume weighted average price (VWAP) of the last half hour of trading. From August 3, 2026, eligible stocks close through a call auction: orders are collected over a fixed window and then matched together at one equilibrium price, which becomes the closing price.
CAS is being rolled out in phases. It currently applies to stocks in the cash segment on which derivative (f&o) contracts are available. Stocks outside the F&O segment are not affected at all and still close at 3:30 PM — so the two groups now have different closing times, which is the single most important thing to take away from this page.
Continuous trading now ends 15 minutes earlier. The closing price comes out of the auction, not the last traded price.
| Session | Timing (IST) |
|---|---|
| Pre-Open Session | 9:00 AM – 9:15 AM |
| Continuous Trading | 9:15 AM – 3:15 PM |
| Closing Auction Session (CAS) | 3:15 PM – 3:35 PM |
| Post-Close Session | 3:50 PM – 4:00 PM |
No change to how these stocks trade or close, apart from the shifted post-close window.
| Session | Timing (IST) |
|---|---|
| Pre-Open Session | 9:00 AM – 9:15 AM |
| Normal Trading | 9:15 AM – 3:30 PM |
| Post-Close Session | 3:50 PM – 4:00 PM |
Futures and options continue past the cash-segment auction so positions can be managed against the newly discovered close.
| Session | Timing (IST) |
|---|---|
| Normal Trading (Stock & Index F&O) | 9:15 AM – 3:40 PM |
CAS runs from 3:15 PM to 3:35 PM and is split into four distinct stages. Orders do not execute as you place them — nothing matches until the final stage.
| Stage | Timing | What Happens |
|---|---|---|
| Transition | 3:15 PM – 3:20 PM | Reference price is computed as the VWAP of trades between 3:00 PM and 3:15 PM. No orders are accepted. |
| Order Entry I | 3:20 PM – 3:25 PM | Both market orders and limit orders are accepted. |
| Order Entry II | 3:25 PM – 3:30 PM | Limit orders only. Order entry closes at a random time between 3:28 PM and 3:30 PM. |
| Order Matching | 3:30 PM – 3:35 PM | The exchange computes the equilibrium price. Every CAS trade executes at that single price, which becomes the closing price. |
The order types you can use during the auction are restricted. These catch people out most often:
From September 7, 2026, the pre-open session will keep its 9:00 AM – 9:15 AM window, but order entry will close at a system-driven random time between 9:08 AM and 9:10 AM — the same anti-gaming design used at the close. This is a separate change from CAS and takes effect later.
Nothing changes. CAS is a change to the equity cash segment only. MCX commodity trading hours are unaffected — see commodity market timings for the current schedule.
CAS is a call-auction session that determines the official closing price of a stock. Instead of the closing price being a volume weighted average of the last 30 minutes of trading, orders are collected during a set window and matched at a single equilibrium price. It became effective on August 3, 2026.
It depends on the stock. For stocks that have F&O contracts, continuous trading ends at 3:15 PM and the Closing Auction Session runs from 3:15 PM to 3:35 PM. For all other stocks, normal trading continues until 3:30 PM as before. Stock and index F&O contracts trade until 3:40 PM.
CAS is being introduced in a phased manner. Initially it applies to cash-segment stocks on which derivative (F&O) contracts are available. Stocks outside the F&O segment are not affected and continue to close at 3:30 PM.
Yes, but only in the first order-entry window, from 3:20 PM to 3:25 PM. Between 3:25 PM and 3:30 PM only limit orders are accepted. Stop-loss orders and disclosed-quantity orders are not allowed at any point during CAS.
Order entry in the second window closes at a system-driven random time between 3:28 PM and 3:30 PM. Because there is no fixed final second, no participant can flood the order book at a predictable moment to influence the closing price.
The reference price is the volume weighted average price (VWAP) of trades executed in the stock between 3:00 PM and 3:15 PM. If no trade takes place in that window, the last traded price of the day is used; if there is no trade at all that day, the previous trading day’s closing price is used.
The price band during CAS is ±3% from the reference price of the stock. For stock futures, the same ±3% band applies from 3:15 PM to 3:40 PM to keep the derivatives segment aligned with the cash segment.
Yes. The post-close session for the equity cash segment now runs from 3:50 PM to 4:00 PM.
Yes, but separately and later. From September 7, 2026, the pre-open session stays 9:00 AM to 9:15 AM, but order entry will close at a system-driven random time between 9:08 AM and 9:10 AM, aligning it with the CAS design.
No. CAS is a change to the equity cash segment only. MCX commodity trading hours are unaffected.
Source: NSE circular NSE/CMTR/73362 dated March 18, 2026 — “Operational guidelines and Standard Operating Procedure (SOP) on Introduction of Closing Auction Session (CAS) in the Equity Cash Segment”, issued under SEBI circular SEBI/HO/47/11/11(3)2025-MRD-POD2/I/2765/2026 dated January 16, 2026. Timings are subject to further exchange circulars.
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