Revised Pre-Open Session: New Rules, Timings and Key Changes

The first few minutes of trading can see sharp price movements as market participants react to overnight news and changing conditions. To support orderly opening price discovery and align the process with the Closing Auction Session (CAS), the exchange has revised its 15-minute pre-open market framework.

Effective September 7, 2026, the revised pre-open session will operate through a call auction mechanism from 9:00 AM to 9:15 AM for eligible index and single-stock futures. The session will follow defined stages for order entry, order matching and opening price discovery.

Here is what the new timings and rules mean for traders/investors.

What Is the Futures Pre-Open Session?

The equity derivatives pre-open session is a 15-minute session held before the continuous trading session begins. It runs from 9:00 AM to 9:15 AM and uses a call auction mechanism to determine the opening price of eligible futures contracts.

During this session, orders are first collected and then matched at a single equilibrium price, which becomes the opening price for the day.

However, the session does not apply to all FnO contracts. It covers eligible index futures and single-stock futures, while options and spread contracts are excluded.

Which Futures Instruments are Covered?

The session applies to:

• Single-stock futures
• Index futures

For most of the contract cycle, it applies only to current-month futures. During the last five trading days before current-month expiry, it also extends to eligible next-month futures. Far-month futures are outside its scope.

It does not apply to options or spread contracts on indices and stocks. It is also not conducted in futures of an underlying security on its ex-date for a corporate action arising from a scheme of arrangement.

What Are the Revised Pre-Open Session Timings?

The overall pre-open timings remain the same, i.e. 9:00 AM to 9:15 AM, but the revised framework changes what traders can do within the order-entry window.

How Does the Revised Pre-Open Session Work?

The pre-open session works through a call auction rather than continuous matching. Orders first accumulate during the collection period.

The process can be understood in four stages.

1. Orders are collected: Traders submit eligible orders during the prescribed windows. Orders can be modified or cancelled subject to the applicable time and order-type restrictions.
2. Indicative information is calculated: Based on the order book, the exchange calculates information including the indicative equilibrium/opening price, total buy and sell quantities, and the percentage change in the indicative equilibrium price from the previous close.
3. A single opening price is determined: Instead of trades occurring continuously at multiple prices, eligible orders are matched at the equilibrium price determined by the auction.
4. The market transitions to regular trading: After matching and trade confirmation, the 9:12–9:15 AM buffer allows the system to transition to the continuous trading session.

This separation between order collection and order matching is the defining feature of the call-auction mechanism.

How Is the Opening Price Determined?

The opening price is based on demand and supply in the pre-open order book. The exchange follows a sequence of criteria to identify the equilibrium price.

First, the system identifies the price at which the maximum quantity can be executed.

– If more than one price qualifies, it selects the price with the lowest absolute unmatched order quantity, or minimum order imbalance.

– If multiple prices still qualify, the equilibrium price is the one closest to the previous day’s closing price. Exchange also specifies how the calculation works when the previous close lies at the midpoint of two qualifying prices and how the reference price is handled following a corporate action. Both market and limit orders are considered when calculating the equilibrium price.

Once discovered, this equilibrium price becomes the contract’s opening price for the day.

There are two special situations:

• If only market orders exist on both the buy and sell sides, orders are matched at the base price, which becomes the opening price.
• If no price is discovered during pre-open, the first trade price in the normal market becomes the opening price.

How Are Orders Matched During the Pre-Open Session?

Once order collection ends, eligible orders are matched at the single equilibrium price.

However, the exchange specifies a clear priority sequence.

• Eligible market orders are matched against one another based on time priority.
• Remaining eligible market orders are matched against limit orders according to the relevant time-and-price priority.
• Remaining limit orders are then matched against other limit orders using price-time priority.

Market orders therefore receive priority over limit orders in the matching sequence.

Once the matching period begins, order modification, order cancellation, trade modification and trade cancellation are not permitted. The exchange also states that trades executed during pre-open cannot subsequently be cancelled through a trade-cancellation request.

What Happens to Unmatched Pre-Open Orders?

An order does not necessarily disappear simply because it was not executed during the auction.

The treatment depends on whether it was a limit or market order.

Traders cannot modify or cancel these outstanding orders in the interval before the normal market starts.

What Are the Key Pre-Open Session Rules?

Beyond timings and price discovery, several operational rules determine how orders behave during the session.

Here are the rules traders should know:

Are Margins Checked During Pre-Open?

Yes, the exchange states that every pre-open order is validated against the applicable margin requirements and available capital before acceptance.

If sufficient capital is not available to meet the margin requirement, the order is not accepted into the pre-open session.

What Information Can Traders See During Pre-Open?

The session also provides indicative market information before the opening price is finalised.

The exchange states that the NEAT Trading Terminal disseminates information such as:

• Indicative equilibrium price
• Indicative tradable quantity at that price
• Cumulative buy and sell quantities
• Indicative imbalance quantity at the equilibrium price
• Imbalance based on outstanding market-order quantities

How Is the Pre-Open Session Different From Normal Trading?

The biggest difference is how and when trades are matched.

Final Thoughts

The revised pre-open framework introduces a defined opening-price discovery process for eligible index and stock futures, with distinct windows for market orders, limit orders, matching and transition to continuous trading.

For traders, the key is to understand which contracts qualify and what actions are permitted at each stage, particularly around the 9:05 AM market-order restriction and random closure of order collection. Before placing a Futures order, it is also important to consider margins, leverage and the risks associated with derivatives.

Revised Pre-Open Session : FAQs