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Introduction of Pre-Open Session in Equity Derivatives (F&O) Segment

3 December 2025

Dear Clients,

We wish to inform you that National Stock Exchange of India Ltd. (NSE) and Bombay Stock Exchange Ltd. (BSE) have announced the introduction of a Pre-Open Session in the Equity Derivatives (F&O) Segment, effective Monday, December 8, 2025.

This implementation is in line with the directions issued by SEBI under its Circular SEBI/HO/MRD/TPD-1/P/CIR/2025/79 dated May 29, 2025, regarding “Measures for Enhancing Trading Convenience and Strengthening Risk Monitoring in Equity Derivatives.”

Session Timings

The Pre-Open Session will be conducted through a Call Auction Mechanism, for a total duration of 15 minutes (9:00 AM – 9:15 AM):

1. Order Entry / Collection Period: 9:00 AM – 9:07/08 AM

  • Order entry, modification, cancellation allowed
  • Random closure between the 7th and 8th minute

2. Order Matching & Trade Confirmation: 9:08 AM – 9:12 AM

  • Opening price determination
  • Order matching
  • No order modification/cancellation allowed

3. Buffer Period: 9:12 AM – 9:15 AM

  • Transition to normal market
  • No order addition/modification/cancellation

Eligible Contracts

The Pre-Open Session will apply to:

  • All current-month futures contracts (Stock Futures & Index Futures)
  • Next-month futures contracts during the last 5 trading days before expiry of current-month futures

Not Applicable To:

  • Calendar spread futures & options
  • Contracts on ex-date of corporate action
  • Far-month contracts

Market Parameters

  • Lot size, tick size & price band: Same as normal market
  • Book type: “PO” for Pre-Open

Trading Session Structure

1. Order Collection Period

  • Limit & Market orders allowed
  • Stop-loss & IOC orders not permitted
  • Indicative price & quantities displayed on NSE/BSE

2. Order Matching Period

  • Matching at equilibrium price, which becomes the opening price
  • Matching priority:
    1. Limit orders with limit orders
    2. Remaining limit orders with market orders
    3. Remaining market orders with market orders

3. Opening Price / Equilibrium Price Rules

  • Price with maximum executable volume selected
  • If multiple prices qualify → price with minimum imbalance
  • If no price discovered → first trade in continuous market becomes opening price
  • If only market orders exist → base price becomes opening price

Unmatched Orders

  • Unmatched limit orders carry forward with original timestamp
  • Unmatched market orders convert to limit orders at equilibrium price

Risk Management & Controls

Applicable Controls

  • Self-Trade Prevention (STPC) active during order collection
  • Orders without required margin will be rejected

Not Applicable Controls

  • NSE: Market Price Protection (MPP) for index futures
  • BSE: MPI, LPP, PRC, RTPC
  • Cancel on Logout (COL)
  • Kill Switch (Member/User level)

MPP & LPP will apply after market opens, using equilibrium price as reference.

Data Dissemination

During the Pre-Open Session, NSE & BSE will display:

  • Indicative Equilibrium Price
  • Total Buy/Sell Quantity
  • Percentage change from previous close

Regulatory References