Closing Auction Session, explained

A new way your stock’s closing price is decided

From 3 August 2026, the closing price of many stocks on NSE and BSE will be decided in a new way - through a Closing Auction Session (CAS).

What’s changing

Today, a stock’s closing price is the average price (VWAP) of all trades in the last 30 minutes of the day (3:00–3:30 PM). From 3 August, for eligible stocks, the close will instead be set by a short auction held between 3:15 PM and 3:35 PM. During this window, all buy and sell interest comes together, and a single price — the one at which the maximum number of shares can trade - becomes the official closing price.

How the auction is bounded: the auction has a reference price and a price band.

• The reference price is the VWAP of the stock's own trades between 3:00 PM and 3:15 PM. If there's no trade in that window, the day's last traded price (LTP) is used instead; if there's no trade at all that day, the previous trading day's closing price is used (or the adjusted closing price / base price, in case of a corporate action).
  
• The auction — both the orders that can be placed and the final closing price that gets discovered — is confined to a band of ±3% around this reference price. Orders outside this band are rejected or cancelled.
  

Which stocks, and when

To begin with, CAS applies only to stocks that have F&O (Futures & Options) contracts. All other stocks continue with the current method for now. The change goes live on 3 August 2026.

Why this is happening

A single, transparent closing price that everyone can actually trade at is the global standard - major markets like the NYSE and London Stock Exchange already work this way. It reduces the chance of a few last-minute orders distorting the close, and gives funds that track indices a fairer reference price. SEBI and the exchanges are bringing Indian markets in line with this approach.

What it means when you trade on Kotak Neo

For most of your trading day, nothing changes - you trade exactly as you do now up to 3:15 PM. The differences appear only in the final minutes, and only for eligible stocks:

• Order types: Once the auction opens for entry, only limit and market orders are accepted. Stop-loss and disclosed-quantity orders can’t be placed in this window.
  

• Intraday auto square-off: Auto square-off timing for equity cash segment will be updated to 3:05 PM and for F&O segment at 3:25 PM.
  

• The price you see: The continuously updating last traded price for F&O stocks pauses during 3:15 to 3:20 pm. From 3:20 pm onwards, you’ll see an indicative closing price that updates as orders come in. The official close is confirmed at the end of the window (around 3:35 PM). Index values (NIFTY,BANKNIFTY, SENSEX and BANKEX) continue to update with an indicative closing price throughout CAS.
  

• F&O timing: Equity derivatives (F&O) will trade until 3:40 PM instead of 3:30 PM.
  

• GTT orders will not trigger during CAS.
  

• Open orders at the transition: any unexecuted limit order from the regular session is automatically carried forward into the auction. Stop-loss orders, iceberg (disclosed-quantity) orders, and any order priced outside the ±3% band are automatically cancelled at the transition, with an on-screen message explaining why.

• Stock futures aren't halted, but their price band is reset: F&O trading itself is never paused - it runs continuously through the CAS window and up to 3:40 PM. What changes is the price band each stock future can trade within: starting 3:15 PM, the exchange recalculates a fresh reference price for each future (based on that future's own VWAP between 3:00–3:15 PM) and resets its band to ±3%, in line with the cash-market band. This re-banding is rolled out sequentially across contracts rather than all at once, so it doesn't happen instantaneously at 3:15 PM. Any resting order that falls outside the revised band is cancelled as its contract is re-banded, with a system message.

• F&O's own closing-price window also shifts: separately from CAS, the VWAP window used to calculate F&O contracts' own closing prices moves from 3:00–3:30 PM to 3:10–3:40 PM, in line with the extended F&O close.

The auction, minute by minute

The 20-minute window (3:15–3:35 PM) isn’t one continuous slot — it moves through distinct stages, each with different rules:

*Order entry actually closes at a random moment between 3:28 and 3:30 PM, decided by the exchange’s system — not exactly at 3:30 — so that no one can time an order to the very last second.

In short: if you’re placing an order between 3:15 and 3:20 PM on an eligible stock, it won’t go through.

This freeze applies only to the cash market. F&O trading on the same underlying is not paused at any point - it continues without interruption right through to 3:40 PM; only its price band is refreshed as described above.

What you need to do

Nothing, for the most part. Keep trading as usual. If you place orders in the last 15–20 minutes of the day, just keep the points above in mind. When the auction is live, the Kotak Neo app and Website will guide you with clear banners and order rejection messages, so you always know what’s happening.