9:00–9:15 am
Pre-open: one price from many orders
The 15-minute pre-open has three parts: about ten minutes in which orders are collected but not traded, two minutes in which the exchange finds a single price, matches orders and confirms trades, and a three-minute buffer before continuous trading.
The schedule since 7 September 2026
The pre-open session shall be conducted using call auction mechanism for duration of 15 minutes i.e., from 9:00 am to 9:15 am.
(this FAQ shall be applicable w.e.f. September 07,2026)
NSE’s comparison table from the FAQ, written before 7 September 2026 (headings and times as printed; “(*)” marks a random closure).
| Session | Current Time | Revised Time |
|---|---|---|
| Order Entry Period | 9:00 am - 9:08 am (*) | 9:00 am - 9:05 am; 9:05 am - 9:10 am (*) |
| Order Matching & trade Confirmation Period | 9:08 am (*) – 9:12 am | 9:10 am (*) – 9:12 am |
| Buffer Period | 9:12 am - 9:15 am | 9:12 am - 9:15 am (no change) |
Order entry, order modification, order cancellation period only for limit orders.
(*) system driven random closure in the last 2 minutes
In plain words
From 9:00 to 9:05 am any order may be placed. From 9:05 only limit orders can be placed or changed, and order entry stops at a random moment in the last two minutes before 9:10 am, so nobody knows the exact last second. Matching follows straight away, and the last three minutes are a buffer before continuous trading at 9:15.
How the open price is chosen
The equilibrium price is the price at which the maximum volume is executable.
In case more than one price meets the said criteria, the equilibrium price is the price at which there is minimum order imbalance quantity (unmatched order quantity).
In case more than one price has same minimum order imbalance quantity, the equilibrium price is the price closest to the previous day’s closing price.
In case the previous day’s closing price is the mid -value of pair of prices which are closest to it, then the previous day’s closing price itself is taken as the equilibrium price.
Market orders shall be given priority over limit orders.
In plain words
Three tests in order: the price that lets the most shares trade; if several tie, the one with the smallest leftover imbalance; if still tied, the one nearest the previous close. Market orders count at every price, because they accept any price. If the previous close sits exactly midway between the two nearest candidate prices, NSE takes the previous close itself.
A worked auction (invented stock)
A sample stock closed yesterday at ₹250.00. These are all the orders in the pre-open book:
Buy orders
- Market order: 200 shares
- ₹251.00: 300 shares
- ₹250.50: 400 shares
- ₹250.00: 500 shares
- ₹249.50: 300 shares
Sell orders
- Market order: 100 shares
- ₹249.50: 300 shares
- ₹250.00: 400 shares
- ₹250.50: 600 shares
- ₹251.00: 500 shares
This site tests each limit price that appears in the book (its modelling choice; NSE’s text does not list candidate prices). For each price in the book: how many shares buyers want at that price or better (buy at or above), how many sellers offer at that price or better (sell at or below), how many could trade (the smaller of the two) and the imbalance.
| Price | Buy at or above | Sell at or below | Tradable | Imbalance |
|---|---|---|---|---|
| ₹249.50 | 1,700 | 400 | 400 | 1,300 |
| ₹250.00 | 1,400 | 800 | 800 | 600 |
| ₹250.50 | 900 | 1,400 | 900 | 500 |
| ₹251.00 | 500 | 1,900 | 500 | 1,400 |
In plain words
The most shares — 900 — can trade at ₹250.50, so that is the equilibrium price and the stock opens there. No tie, so the second and third tests are not needed. Sellers offered 1,400 shares at or below that price, so 500 shares of sell orders stay unmatched in the auction.
If no price is found, and other cases
In case of no price is discovered in pre -open session, the price of first trade in the normal market is the open price.
Special term orders like Stop loss (SL), Immediate or Cancel (IOC) and Disclosed Quantity (DQ) shall not be allowed.
In case of index-based market-wide circuit filter breach or any outage (stopping of trading, either suo moto by Exchange or by the virtue of reasons beyond control of stock exchange ), the market shall open with a pre-open session, and its timings shall be informed separately on that day.
Futures have a pre-open too
The pre-open shall be applicable for current months futures contracts only on both single stocks and indices. However, in the last five trading days before the current month expiry, this session shall be extended to next-month futures contracts.
Members are required to note that the changes in pre-open call auction framework in the Equity derivatives segment, shall be effective in LIVE from September 07, 2026.