Pre Open Session: Timings, Process & Key Changes Effective 7 September 2026

Did you know, you can trade before the stock markets officially open? Since 2010, the National Stock Exchange (NSE) and the Bombay Stock Exchange (BSE) have allowed for a 15-minute pre-open or pre-market session. This helps to reduce price volatility right at the opening of the market. The market can then open at a price set by genuine supply and demand for security instead of being driven by the price set by the first trade. 

Since December 2025, the session also covers equity derivatives. And from Monday, 7 September 2026, its internal structure changes. If you only want the changes, skip to “What Does the Pre-Open Session Involve? Key Changes Effective 7 September 2026”.

Key Takeaways

What Is Pre Open Session?

Pre-Open Session is a short trading window before regular trading begins where all buy and sell orders are collected and matched at a single price. Its main goal is to determine the official opening price for stocks and reduce early market volatility caused by overnight news or global market movements. 

Here is the problem it solves. Suppose a company announces disappointing results at 8 PM. By 9:00 AM the next morning, thousands of investors want out, and thousands of bargain-hunters want in, and nobody knows where the price should be. Without a pre-open session, the first trade at 9:15 AM sets the opening price — and that single trade might be tiny, mispriced, or both. Everyone else then reacts to a number that was never representative. 

The pre-open session fixes this by collecting all those orders first, matching them together, and announcing a single opening price before regular trading starts. 

What Are the Advantages of Pre Open Session? 

What Are the Timings of Pre Open Session? 

The pre-open session runs for 15 minutes, from 9:00 AM to 9:15 AM. Regular trading begins at 9:15 AM. Timings are the same on the NSE and the BSE. 

Those 15 minutes are not one continuous block. They are divided into an order entry period, an order matching period, and a buffer period. The split within those 15 minutes changes on 7 September 2026 — full detail is in the next section. 

What Does the Pre-Open Session Involve? Key Changes Effective 7 September 2026

Three phases. Here is what happens in each, under the framework effective 7 September 2026. 

9:00 AM – 9:10 AM: Order entry period 

Orders are collected, but nothing is executed. You can place, modify and cancel orders throughout — with one boundary in the middle: 

Throughout the whole period, the exchange publishes an indicative opening price that updates as orders arrive, along with total buy and sell quantities and the imbalance between the two sides. 

Why does order entry close at a random moment? So, the last second cannot be gamed. If everyone knew the exact instant the order book shut, some participants would flood it with orders at the final moment to nudge the opening price in their favour. Because nobody knows when the window closes, that tactic does not work. It is a design feature, not a glitch — so do not plan to place or cancel an order in the final seconds. 

9:10 AM – 9:12 AM: Order Matching and Trade Confirmation

This time slot is considered to be crucial for setting up the price of a security. The process involves aligning demand and supply prices through a price-matching order to ensure precise transactions between investors looking to buy or sell securities. This system helps in determining the security prices during the normal trading session. Here, unlike the prior time slot, modifications for the placed orders are not permitted in this session. 

Orders that remain unmatched are carried forward automatically into the continuous trading session at 9:15 AM.  

Orders placed during this window are scheduled and sent to the exchange for execution at 9:15 AM.  

9:12 AM – 9:15 AM: Buffer Period 

A short transition to the continuous trading session. Unmatched orders are moved into the continuous market, and at 9:15 AM continuous trading begins. 

You can still place orders during this window on Angel One. They do not participate in the auction — it is already over. They are scheduled and executed after 9:15 AM, once the continuous trading session opens. 

What is not Changing?

What is not changing: the session length, market timings, and the 9:15 AM open; Anything about the trading day after 9:15 AM. How the opening price is calculated — orders are still matched at a single equilibrium price using the same demand-and-supply logic; and what happens to unmatched orders. Margin validation still applies to every order at the point of entry. If you do not place orders between 9:00 and 9:15 AM, this change does not affect you at all. 

Which Securities are Covered? 

At ₹101, 600 shares can trade — more than at any other price. So, ₹101 is the equilibrium price and the day's opening price, and orders that execute do so at ₹101. That is the whole point of a call auction: one price for everyone. 

What if two prices tie? The exchange works down a fixed set of tiebreakers: first the price with the smaller imbalance of unmatched quantity, then the price closest to the previous day's close, and if the previous close sits exactly between two candidates, the previous close itself. 

What if no price can be discovered? If no orders can be matched at all, there is no opening price from the auction, and the first trade in the continuous trading session becomes the day's opening price instead. 

Are There any Risks to Pre Open Session? 

Who Can Trade in the Pre Open Session? 

Any Angel One customer with an active trading account can place orders in the pre-open session — there is no separate activation to request. Simply place your order between 9:00 AM and the close of the order book. 

That said, the session suits some purposes better than others. It is most useful if you have a specific view on how a stock should open — after results, a corporate announcement, or a sharp overnight move in global markets. If you do not have that view, there is no disadvantage to waiting for regular trading at 9:15 AM, where liquidity is far deeper and spreads are tighter. Pre open is a tool, not an obligation. 

If you do not have a Demat account to start investing, consider opening with Angel One. We offer a user-friendly platform that enables you to manage your portfolio with one account. Get investing with Angel One! 

Conclusion 

The pre-open session exists, so the trading day starts on a considered price rather than an accidental one. For 15 minutes each morning, the market gathers every overnight opinion, finds the single price at which the most shares can change hands, and opens there. 

From 7 September 2026, the mechanics inside those 15 minutes are a little different: the order entry period splits into two windows, order entry stays open until 9:10 AM, and order matching happens from 9:10 to 9:12 AM. The purpose is unchanged, the session length is unchanged, and the market still opens at 9:15 AM. 

For most investors, that's context rather than a to-do. For anyone who places orders before the bell, one thing is worth knowing: Stop Loss, IOC, and Iceberg orders do not take part in the auction. Angel One still accepts them and schedules them for execution at 9:15 AM.