Every trading day on the NSE and BSE begins with a pre-open session from 9:00 AM to 9:15 AM. During those fifteen minutes the market is not trading continuously. Orders are collected, then matched all at once at a single opening price that the exchange works out. Continuous trading begins at 9:15 AM from that price.
It exists to take the guesswork out of the open. Overnight news, results and global moves all want to express themselves the instant the market opens; letting them collide in a continuous order book would produce a violent, arbitrary first print. Collecting everything first and settling on one price damps that.
What happens in each of the fifteen minutes?
| Window | What you can do |
|---|---|
| 9:00 – 9:05 | Place, modify or cancel both market and limit orders. Nothing executes. |
| 9:05 – until closure | Limit orders only. New market orders are rejected. You can still modify or cancel what you already placed. |
| Random closure, 9:08 – 9:10 | Order entry shuts at a moment the exchange does not announce in advance. |
| 9:10 – 9:12 | The exchange matches orders and confirms trades at the opening price. |
| 9:12 – 9:15 | A buffer. Nothing for you to do; it is the handover into the normal session. |
Two of those deserve a word.
Why market orders stop at 9:05. A market order names no price, so it leans on everyone else's orders to find one. Cutting them off part-way through leaves the back half of the window as pure limit-order business, which is what actually builds the price picture.
Why the close is random. If entry always shut at exactly 9:10:00, the most valuable second of the session would be 9:09:59 — drop in an order too late for anyone to respond to, and walk the price. Closing at an unannounced instant between 9:08 and 9:10 removes that last-second edge.
How is the opening price decided?
The exchange looks for the price at which the largest quantity can actually change hands. This is the equilibrium price, and it is a call auction in the textbook sense.
Say the pre-open for Bharat Paints Ltd collects orders spread across a price range. The exchange tests each candidate price and asks one question: at this price, how many shares would match?
| Candidate price | Shares that would match |
|---|---|
| ₹412 | 40,000 |
| ₹415 | 62,000 |
| ₹418 | 35,000 |
₹415 wins, and becomes the opening price. Every trade struck in the auction executes at ₹415 — including the order from someone who was willing to pay ₹418, and the one from someone happy to sell at ₹412. A single price for everybody is the point of the exercise.
If two candidate prices would match the same quantity, the exchange picks the one leaving less unmatched quantity behind. If that is still tied, it takes the one closest to the previous day's closing price. And if no trades happen in the pre-open at all, there is no discovered price — the day's first trade in the normal session becomes the opening price instead.
Which orders get matched first?
This changed on 7 September 2026. Limit orders used to take priority in pre-open matching; market orders now go first.
Once the equilibrium price is fixed, matching runs in three passes:
- Market against market, in the order the orders arrived.
- Market against limit — eligible limit orders are taken best-price-first, and where two name the same price, the earlier one goes first.
- Limit against limit, on the same price-then-time basis.
Every one of those matches settles at the single opening price, whatever price the individual order named.
What happens to my order if it doesn't match?
Nothing is lost — it moves into the normal session at 9:15.
- An unmatched limit order carries forward as it stands, keeping its original timestamp, so it does not lose its place in the queue.
- An unmatched market order is converted into a limit order at the discovered opening price and carried forward. This is why a pre-open market order can behave like a limit order once the market opens — see Why does my market order in the pre-open session change to a limit order?
- If the auction found no opening price at all, market orders carry forward at the base price — the previous day's close.
Does the pre-open apply to futures too?
Yes, on the same 9:00–9:15 clock and with the same phases, but the list of contracts it covers is narrower:
- Current-month futures on both stocks and indices take part.
- In the last five trading days before expiry, next-month futures join them, so the roll has a discovered price too.
- If a futures contract's underlying stock has a corporate action that day — a merger or demerger, for instance — that contract sits the session out.
This is not the Special Pre-Open Session
They are different sessions with confusingly similar names.
| Pre-open session | Special Pre-Open Session | |
|---|---|---|
| When | 9:00 – 9:15, every trading day | 9:00 – 10:00, one day only |
| Applies to | The whole market | A single stock with no recent price — an IPO's first day, or a relisting |
| Order types | Market and limit (market until 9:05) | Limit only |
| Normal trading starts | 9:15 AM | 10:00 AM |
Things to keep in mind
- An order sitting unexecuted before 9:15 is not a stuck app. It is waiting for the auction. See Why do I experience delays in order placement during market opening?
- You cannot control your fill price with a pre-open market order. It fills at whatever the auction discovers. If you need a ceiling or a floor, use a limit order.
- The opening price is not a prediction. It reflects only the orders that happened to be in the book during those fifteen minutes, which on a quiet morning can be very few.
For the exchange's own description of the session, see NSE's equity market pre-open page.