On Monday the market opens on a different clock: the pre-open session is rebuilt from 7 September 2026
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From Monday 7 September 2026 the NSE pre-open session runs as four stages inside 9:00–9:15 am. Market orders get five minutes instead of eight.
On 7 September 2026 the NSE pre-open session changed. That is the first part of the trading day. It no longer runs the way it ran on Friday 4 September 2026. The window for a market order is now 5 minutes, not 8. Once it shuts, a market order can no longer be entered, changed or cancelled for the rest of the session. Limit orders keep going for another 5 minutes. The book then shuts at a moment the system picks at random. Continuous trading still starts at 9:15 am. The opening bell has not moved. Everything inside it has.
- The date is fixed in writing. SEBI's circular says the pre-open changes are implemented from 7 September 2026. Both of NSE's 4 September 2026 notices name live trading on that Monday, after a mock session on the Saturday.
- Market orders lose 3 minutes of the session. The window is now 9:00 am – 9:05 am, not 9:00 am – 9:08 am.
- After that stage a market order cannot be placed, modified or cancelled. The order book stays open to limit orders until a random moment between 9:08 am and 9:10 am.
- The equity cash segment and the equity derivatives segment change on the same date. Continuous trading still begins at the time it always did.
Pre-open session time: what is different on Monday morning
Until Friday the pre-open collected orders in one block and then matched them. From Monday it collects them in two blocks. Each block has its own rules, and matching starts later. The table is the whole change. Everything after it comes from the two circulars. They set the rules inside each stage.
| What the stage is for | Up to and including 4 September 2026 | From 7 September 2026 |
|---|---|---|
| Orders can be placed, changed and cancelled — limit and market orders both | 9:00 am – 9:08 am | 9:00 am – 9:05 am |
| Limit orders only. Market orders can no longer be changed or cancelled | No such stage — the outgoing session did not have one | 9:05 am – 9:10 am |
| The opening price is worked out and matched trades are confirmed | 9:08 am – 9:12 am | 9:10 am – 9:12 am |
| Buffer, carrying orders across into continuous trading | 9:12 am – 9:15 am | 9:12 am – 9:15 am |
| Continuous trading begins | 9:15 am | 9:15 am |
The session is the same length. The order window inside it is now split in two. The half that takes a market order is the shorter one.
The 5 minutes that changed the most
The change that matters most in practice is about market orders. From 9:05 am the exchange stops accepting them. It also stops accepting changes and cancellations to the ones already in the book. A market order placed at 9:00 am is therefore stuck there for the rest of the auction.
- Limit orders and market orders both count towards the opening price, in the stage where each is accepted.
- Quantity cannot be hidden. An order must be disclosed in full, so iceberg orders are not accepted.
- The exchange's special-term order types are not accepted at all. That rules out the order that waits for a trigger price. It also rules out the immediate-or-cancel order and the disclosed-quantity order.
- Algorithmic market orders are accepted only during the first 5 minutes. That is the one stage in which market orders are allowed.
- The exchange rejects a market order placed after that stage. The trading terminal shows the message “Market orders are currently not allowed.”
- A trade executed in the pre-open cannot be cancelled. The request is rejected by the system.
How the opening price gets chosen
Nothing executes while orders are being collected. At the end the system looks for one price. It is the price at which the largest quantity can be matched. Every trade in the auction then happens at that one price. That mechanism is not new. What the circular restates is the order in which the matching engine works through the book.
- Eligible market orders are matched against each other first, in time order, at the final opening price.
- Whatever is left of them is matched against limit orders, in price-then-time order.
- The remaining limit orders are matched among themselves, in price-then-time order.
The order entry period does not end on the clock. The system shuts it somewhere between 9:08 am and 9:10 am. Matching begins as soon as it does. Nobody can know the exact instant in advance, and that is the design.
A random close means nobody can plan around the last minute of the order window. That is the point of it.
What the screen shows while it runs
There is no last traded price during a call auction, because nothing has traded. The exchange publishes a different set of numbers instead. The circulars list it item by item.
- The indicative opening price of the stock, and the quantity tradable at it.
- The indicative cumulative buy and sell quantity.
- The indicative imbalance at the equilibrium price.
- The indicative imbalance counting market orders alone.
- The indicative opening value of the indices, NIFTY 50 included.
The last item is the one worth noticing. The exchange publishes an indicative opening value for the indices, NIFTY 50 included, while the auction is still collecting orders. Indicative is the key word. It is what the index would open at if the auction closed on the current book. It is not a value anything traded at.
Why the pre-open session moved at all
This is the second half of a circular whose first half already landed. The same SEBI document brought in the closing auction in the cash segment on 3 August 2026. It then rewrote the pre-open to match. Same stage structure, same random close, same two-block order window, at the other end of the day.
From Monday both ends of the trading day are call auctions built the same way. That symmetry is the reason the change exists.
What this post does not cover
- This post describes what the circulars say. It does not describe how any one broker shows the pre-open in its order window. Nor does it say which of these order types a broker chooses to offer at all.
- The times are the exchange's published schedule for an ordinary trading day. A special session has its own timings, notified separately. So does a day that reopens after a market-wide halt.
- Later circulars can amend any of this. Each source below carries the date a human last read it.
- Market structure explains who trades where and how orders meet. It does not predict the next price.
The documents this post is built on
Each card is a real document, named by its own reference number and date, with the part of this post that rests on it and the day a human last opened it.
The framework itself. Para 5.1 rewrites paragraph 17.1 of the SECC master circular dated 30 December 2024. Para 17.1.2 gives the four stages and their start times. Para 17.1.3 gives the random close of the order entry period. Para 17.1.4 says which order types count and which are refused. Para 17.1.9 gives matching priority. Para 17.1.14 says what is published while the session runs. Para 6.2 carries the implementation date.
The exchange's own before-and-after table for the cash segment, and the operating rules underneath it. Those rules name the order types refused. They confine algorithmic market orders to the first five minutes. They give the exact message a late market order is rejected with. They state that a pre-open trade cannot be cancelled. They also give the matching sequence, and the table of what the terminal displays during the session.
Published the day before the mock session. It confirms the changes go live. It names the mock session on Saturday 5 September 2026. It refers twice to live trading on Monday 7 September 2026. It also bundles two unrelated exchange-traded-fund circulars into the same go-live, which this post does not describe.
This is the sentence that puts the derivatives segment on the same date. It reads: the changes in the pre-open call auction framework in the equity derivatives segment shall be effective in live from 7 September 2026. It names NSE/FAOP/74970 dated 1 July 2026 as the circular behind it. That document was not opened for this post, and nothing here rests on it.
Sources
If a figure here disagrees with its source, trust the source.
Make it concrete
The closing auction, explained
The other half of the same circular, live since August, at the other end of the trading day.
Open →Glossary: circuit limits
The price band framework the auction operates inside.
Open →NSE market & clearing calendar 2026
Which days this schedule applies to, and which days it does not.
Open →Frequently asked
What are the NSE pre-open timings from 7 September 2026?
The session still runs 9:00 am to 9:15 am IST. Inside it: 9:00 am – 9:05 am for limit and market orders, 9:05 am – 9:10 am for limit orders only with a random close in the last two minutes, 9:10 am – 9:12 am for matching, and 9:12 am – 9:15 am as a buffer into continuous trading.
Can a market order still be placed in the pre-open?
Yes, but only during 9:00 am – 9:05 am. After that the exchange rejects new market orders. It also does not accept changes or cancellations to the ones already there.
Does the market still open at 9:15 am?
Yes. Continuous trading still begins at 9:15 am IST. The change moves the stages inside the pre-open. Nothing else about the start of the day moves.
Does this apply to futures and options as well?
Yes. NSE's 4 September 2026 notice covers the equity derivatives segment. It says the pre-open changes there are effective in live from the same Monday.
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