Why did the closing price of your stock look different after 3:30 PM? SEBI is changing how the daily closing price is calculated. Under its 16 January 2026 circular, the closing price will come from a dedicated Closing Auction Session, a short call auction at the end of the day, instead of the volume-weighted average price of the last 30 minutes of trading. You do not have to do anything; this is an exchange-level change that affects how one number is computed, not how you buy or sell.
The daily “closing price” is one of the most important numbers in the market. It is not the last trade of the day. Until now it has been calculated as a volume-weighted average. SEBI is moving that calculation to a call auction.
| Old method (VWAP) | New method (Closing Auction Session) |
|---|---|
| Closing price = volume-weighted average price of the last 30 minutes of continuous trading | Closing price = single clearing price discovered in a dedicated end-of-day call auction |
| Based on many trades spread across the window | Based on one auction that matches all buy and sell orders at one price |
| Easier for a large last-minute order to nudge the average | Harder to move, because all orders compete to set one fair clearing price |
| Used today for NAV, indices, F&O settlement and next-day circuit limits | Same uses, but the number is now auction-discovered |
The closing price quietly drives a lot of your money, even if you never trade near 3:30 PM:
Because so much rides on one number, the way it is calculated matters to ordinary investors, not just to traders.
SEBI has issued a circular introducing a Closing Auction Session (CAS) in the equity cash segment.
In plain terms, the closing price will be discovered through a dedicated auction at the end of the trading day rather than by averaging the last 30 minutes of normal trading. The circular also makes certain modifications to the existing Pre-Open Auction Session that runs before the market opens.
The detailed clock timings of the auction phases, and the date from which each phase goes live for which group of stocks, are being implemented in a phased manner by the stock exchanges under SEBI's framework. For the exact session timings and the go-live schedule, rely on the operating guidelines published by your exchange, the NSE or the BSE, rather than on any unofficial summary.
A call auction is different from normal continuous trading. In continuous trading, every order is matched the instant a willing buyer and seller meet, so prices change tick by tick. In a call auction:
Because every order competes to set the same clearing price, a call auction is harder for any single large order to distort. That is the main reason SEBI is using it for the close: a single auction-discovered price is more robust and reduces the “tracking error” that index funds suffer when the closing number can be nudged.
Do you need to do anything? No, and here is why. This is an exchange-level change in how one price is computed. You do not need to update your demat account, change your SIP, switch funds, or place any special order. There is no form to file and no fee. Just be aware that near the very end of the day there is a short auction window, so if you want to trade right at the close, follow your broker's guidance on placing orders into the closing auction.
Real-life example. Kashvi Pathak runs a monthly SIP into a Nifty index fund. She never trades intraday; she just lets her units accumulate. One evening she notices that the closing price of a heavyweight stock is a little different from its last visible trade, and worries her fund is mispriced. In fact, her exchange has begun discovering the closing price through the new Closing Auction Session under the SEBI circular dated 16 January 2026. Her NAV is still struck from the closing price exactly as before, only the closing number is now auction-discovered and harder to distort. Kashvi does nothing: no form, no fee, no switch. Her SIP continues, and her index fund actually tracks its benchmark a touch more closely because the closing price is more robust.
No. Your normal buy and sell orders during market hours work exactly as before. The change is only in how the single end-of-day closing price is calculated. If you want to trade right at the close, follow your broker's instructions for placing orders into the closing auction.
Your NAV is still calculated from the closing price, as it always has been. CAS only changes how that closing price is discovered, moving it to an auction. A cleaner closing price means your NAV reflects a fairer end-of-day value, but there is nothing you need to do.
SEBI introduced CAS through circular HO/47/11/11(3)2025-MRD-POD2/I/2765/2026 dated 16 January 2026. The exact session timings and the phased go-live dates for different groups of stocks are being implemented by the stock exchanges. For the precise schedule, check the operating guidelines from your exchange, the NSE or BSE, rather than any unofficial summary.
A single auction clearing price is harder for one large last-minute order to distort than a volume-weighted average of many trades. A more robust closing price reduces manipulation risk and lowers the tracking error that index funds and ETFs face, which benefits ordinary passive investors.
VWAP stands for volume-weighted average price. The closing price was earlier calculated as the volume-weighted average of all trades in the last 30 minutes of continuous trading, giving more weight to prices at which more shares traded.
No. This is an exchange-level change in how a price is computed. There is no form, no fee, and no action required from you. Just stay aware of the short auction window near the close if you trade at that time.