Special Pre-Open session

The special pre-open session is applicable to the below type of securities:

  • IPOs securities - first day of trading. This also includes SME IPOs
  • Re-listed Securities first day of recommencement of trading. (as defined under para 1(C) of SEBI circular no. SEBI/Cir/ISD/1/2010 dated September 2, 2010)
  • Stocks having derivatives contracts on the Ex-date of trading after undergoing corporate restructuring*

Download Special Pre-Open session FAQs

*Corporate Restructuring: Merger, demerger. Amalgamation, capital reduction/consolidation, scheme of arrangement, in terms of the Companies Act and/or as sanctioned by the Courts, in cases of rehabilitation packages approved by the Board of Industrial and Financial Reconstruction under Sick Industrial Companies Act and in cases of Corporate Debt Restructuring (CDR) packages by the CDR Cell of RBI.

The below are the timings for special pre-open session:

Pre-open2 session



Order Entry Period

9:00 am - 9:45 am (*)

  • Order entry, Modification and Cancellation
  • (*)    System    driven    Random    closure between 44th and 45th minute

Order Matching & trade Confirmation Period

9:45 am(*) - 9:55 am

  • (*) Order matching period will start immediately after completion of order collection period.
  • Opening price determination.
  • Order matching and trade confirmation.

Buffer Period

9:55 am - 10:00 am

  • Transition   from    pre -open    to Normal market
  • Order matching period will start immediately after completion of order collection period.
  • Order will be matched at a single (equilibrium) price which will be open price.
  • Eligible buy limit orders will be matched with eligible sell limit orders
  • During order matching period order modification, order cancellation, trade modification and trade cancellation will not be allowed. The trade details will be disseminated to respective members immediately after matching of trades.
  • The opening price shall be determined based on the principle of demand and supply mechanism.
  • The equilibrium price will be the price at which the maximum volume is executable.
  • The equilibrium price determined in call auction of pre-open 2 session is considered as open price for the day.
  • In case more than one price meets the said criteria, the equilibrium price will be the price at which there is minimum order imbalance quantity (unmatched order quantity). The absolute value of the minimum order imbalance quantity will be taken into consideration.
  • In case more than one price has same minimum order imbalance quantity, the equilibrium price will be the price closest to the base price. In case the base price is the mid-value of pair of prices which are closest to it, then the base price itself will be taken as the equilibrium price.
  • In case of IPO and SME IPO securities:
    1. All unmatched limit orders within applicable price range in the pre-open 2 session will be moved in the normal market session at their limit price on the basis of the price-time priority.
    2. This transfer will be done irrespective of equilibrium price discovered or not.
  • In case of Re-listed Securities:
    1. In case of equilibrium price is determined, all unmatched orders within applicable price range will be moved to the normal market at their limit price on the basis of the price time priority
  • For IPO security:
    1. The security will move to normal market at the base price (issue price) of the security
  • For Relisted security:
    1. If the equilibrium price is not determined, all the orders shall cancelled by the system.
    2. Security will not be available for trading in normal market if equilibrium price is not determined in any of the Exchange
    3. The pre-open 2 session for the said security will be conducted on subsequent trading day.
  • For stocks having derivatives contracts prior to undergoing corporate restructuring:
    1. In case equilibrium price is not discovered, all the outstanding orders shall be cancelled and the stock shall continue to trade in special pre-open session on the first day until the price is determined.
  • No Price bands are applicable in the special Pre-open session.
  • However in order to prevent members from entering orders at non-genuine prices in such securities based on Pre-trade risk control guidelines, the Exchange sets the dummy circuit filter i.e. operating range

The initial dynamic price bands shall be set uniformly in co-ordination with other Exchanges in the range of 25% to 75% as the case may be.

Yes, it shall be flexed in consultation with other Exchanges.

The Exchanges shall flex the operating range / dummy price bands in multiples of 10%.

  • It shall result in price freeze which shall be subsequently cancelled by Exchange.
  • An illustration is provided below for better clarity :
Time Base Price (Rs) Operating Range (Rs) Order Entered at price ( Rs) Result
09:00 am 100 90 - 110 95 Accepted
105 Accepted
85 Will result in price freeze
115 Will result in price freeze
09:10 am 100 75 - 110 80 Accepted
110 Accepted
45 Will result in price freeze
120 Will result in price freeze For Base Price
1 IPOs ( including SME) Issue Price
2 Re-listed Securities a) First day of recommencement of trading Last cum price of existing security on NSE
b) Direct listing / MOU / securities admitted for trading under permitted category Last available price of the security on the respective Exchange
3 Stocks having derivatives contracts on the Ex -date of trading after undergoing corporate restructuring Closing Price of the Last cum date of the scrip
  • Base price is visible in market inquiry screen (F11) on TWS in the field name “Close”.


Terminologies Used:

  • SME - Small and Medium Scale Enterprises
  • IPO - Initial Public Offering
  • MoU - Memorandum of Understanding
  • TWS - Trader Work Station
  • NSE - National Stock Exchange
  • SEBI - Securities and Exchange Board of India
Updated on: 30/09/2019
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