Customer Service FAQs HKEX Auction Sessions

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HKEx Auction Sessions

    Pre-opening Session
    Introduction to the HKEx's Pre-opening Session
  1. The Pre-opening Session is an additional trading session of 30 minutes (9:00 am - 9:30 am HKT), which takes place before the Morning Trading Session. It allows orders entered into the trading system, Automatic Order Matching and Execution System (AMS/3), to be matched and executed by auction at one single price.

    The Pre-opening Session comprises of four different period as follows:

    Trading Status Hong Kong Time Highlights
    Order Input Period (15 minutes)
    Hong Kong Time
    9:00 am - 9:15 am
    Highlights
    • Input of Limit Orders.
    • Price Limit: ±15% of previous closing price (Not applicable to some cases, see note 1)
    • Orders are accumulated in HKEx trading system.
    • Orders may be modified or cancelled.
    No cancellation Period (5 minutes)
    Hong Kong Time
    9:15 am - 9:20 am
    Highlights
    • Input of Limit Orders.
    • Price Limit: Lowest ask & highest bid2 (recorded at the end of Order Input Period)
    • No modification or cancellation of Limit Orders.
    Random Matching Period (2 minutes)
    Hong Kong Time
    9:20 am - 9:22 am
    Highlights
    • Input of Limit Orders.
    • No modification or cancellation of Limit Orders.
    • Orders are matched randomly between 9:20am-9:22am
    • Order will be matched at the final Indicative Equilibrium Price (IEP)3.
    • And no order matching will be conducted if final Indicative Equilibrium Price (IEP) cannot be determined
    Blocking Period (8 minutes)
    Hong Kong Time
    End of Random Matching Period - 9:30 am
    Highlights
    • A break between the Pre-opening and the Continuous Trading Session.
    • No input, modification or cancellation of orders.

    • In the absence of the Previous Closing (e.g. IPO stocks) and stocks resuming from trading suspension, 1st stage price limit checking will be relaxed for Order Input Period
    • In case there is no buy order and/or sell orders recorded at the end of Order Input Period, the 2nd stage price limits will be same as the 1st stage price limits.
    • The final Indicative Equilibrium Price (IEP) will be used as the market-opening price for the corresponding security.
    • All equities, including
      • Depository receipts
      • Investment companies
      • Preference shares; and
      • Staple securities
    • Funds, including
      • Exchange Traded Funds (ETFs) ; and
      • Real Estate Investment Trusts (REITS)
    • Leveraged and Inverse Products.
    • Exclude structured products, debt securities, equity warrants and rights
  3. Orders will be matched in the Order Matching Period at the final Indicative Equilibrium Price (IEP) , at which the maximum number of shares can be traded.
  4. Yes. There might be no order matched in the Pre-opening Session if no Indicative Equilibrium Price (IEP) is determined.

    This can occur when there are only Limit Orders on one side, or Limit Orders on both sides but the highest bid price of the buy Limit Orders is lower than the lowest ask price of the sell Limit Orders.
    5. Our Pre-opening Service
  5. Simply place your Limit Order at anytime between 4:11 pm and 9:22 am HKT. Our trading system will automatically convert your Limit Order into At-auction Limit Order (ALO) and submit it to the HKEx for the Pre-opening Session.
  6. No. Market Order can only be placed and processed in the Continuous Trading Session (9:30 am - 12:00 pm and 1:00 pm - 4:00 pm HKT).
  7. You can change or cancel your order anytime. However, please note that the HKEx have restrictions on order cancellation or modification between 9:15 am to 9:30 am HKT. Therefore, your cancellation or modification requests made during this time will be processed at 9:30 am HKT.
  8. Unfilled orders will continue to be processed as Limit Orders in the market until they are filled, cancelled or expired on the Good-till-date you have specified.
  9. You can have single-day orders processed in the Continuous Trading Session for that day by placing the order any time from 9:22 am to 4:00 pm HKT.
    Closing Auction Session (CAS)
    Introduction to the HKEx's Closing Auction Session (CAS)
  1. The Closing Auction Session allows orders to be entered into the trading system for a single price auction which consists of a reference price fixing period, an order input period, a no cancellation period, and a random closing period as follows:

    Full Day Trading Half Day Frading*
    Reference Price Fixing Period
    Full Day Trading
    4:00 pm - 4:01 pm
    Half Day Frading*
    12:00 pm - 12:01 pm
    Order Input Period
    Full Day Trading
    4:01 pm - 4:06 pm
    Half Day Frading*
    12:01 pm - 12:06 pm
    No Cancellation Period
    Full Day Trading
    4:06 pm - 4:08 pm
    Half Day Frading*
    12:06 pm - 12:08 pm
    Random Closing Period
    Full Day Trading
    4:08 pm - 4:10 pm
    Half Day Frading*
    12:08 pm - 12:10 pm
    *Eves of Christmas, New Year and Lunar New Year
  2. In this period, a reference price which sets the allowable price limit of CAS (±5% from the reference price) is calculated for each CAS security. The reference price is determined by taking the median of 5 nominal prices in the last minute of the Continuous Trading Session and the system will take 5 snapshots on the nominal prices at 15-second interval starting from 15:59:00.
  3. In this period, at-auction orders and at-auction limit orders within the ±5% price limit can be entered on CAS securities. Outstanding orders can also be amended or cancelled during this period.
  4. In this period, at-auction orders and at-auction limit orders can be entered. However, the prices of new at-auction limit orders must be between the lowest ask and highest bid recorded at the end of the Order Input Period (i.e. recorded at 16:06), and no orders can be amended or cancelled.
  5. In this period, the order rules from the No Cancellation period apply, and the market closes randomly within two minutes.
    • All equities, including
      • Depository receipts
      • Investment companies
      • Preference shares; and
      • Staple securities
    • Funds, including
      • Exchange Traded Funds (ETFs) ; and
      • Real Estate Investment Trusts (REITS)
    • Leveraged and Inverse Products.
    7. Our Closing Auction Service
  7. Limit orders not filled in the preceding Continuous Trading Session will be automatically converted into at-auction limit orders in CAS. You can also input new at-auction limit orders before the random closing of the market.
  8. No. Market order can only be placed and processed in the Continuous Trading Session. (9:30 am – 12 pm and 1:00 pm – 4:00 pm HKT)
  9. You can change or cancel your orders during the Order Input Period.
  10. Orders that should expire at the end of the day will lapse. Good Till Date orders not yet expired will be carried forward to the next trading day.
  11. You should cancel your order during the Order Input Period.
    Volatility Control Mechanism (VCM)
  1. The Volatility Control Mechanism is designed to prevent extreme price volatility from trading incidents such as a “flash crash” and algorithm errors, and to address systemic risks from the inter-connectedness of securities and derivatives markets. Many international exchanges have implemented some form of VCM. In the case of HKEX’s VCM, if the price deviates more than a predefined percentage within a specific time frame, it will trigger a cooling-off period for five minutes. This provides a window allowing market participants to reassess their strategies, if necessary. It also helps to re-establish an orderly market during volatile market situations.

  2. VCM is applicable to continuous trading session (CTS), excluding:

    • the first 15 minutes of the morning and afternoon trading session
    • the last 15 minutes of the afternoon trading session
    • the After-Hours Futures Trading session in the derivatives market
  3. In the securities market, the VCM will cover Hang Seng Index (HSI) and Hang Seng China Enterprise Index (HSCEI) constituent stocks (as of 31 May 2016 there were 81 such stocks listed on the Stock Exchange of Hong Kong).

    In the derivatives market, the VCM will cover spot and next calendar month index futures contracts with HSI or HSCEI as their underlying index (currently eight futures contracts).
  4. VCM is NOT a trading halt, nor is it designed to limit the ups and downs of prices of stock or futures contract due to fundamental events.
  5. Maximum of one trigger in the morning session and one in the afternoon session for each instrument to minimize market interruption.
  6. VCM is triggered if a stock (futures contract) is ±10％（±5%）away from the last traded price 5 minutes ago; a 5-minute cooling-off period will start.
  7. Yes. During the cooling-off period, trading is allowed within a pre-defined price band.
    Glossary
  1. An At-auction Limit Order (ALO) is a limit order with a specified price.
  2. Indicative Equilibrium Price (IEP) is the price at which the maximum number of shares can be traded if matching occurs at that time.

    An IEP is calculated during the Pre-opening Session and serves as the market-opening price for the corresponding security.

    It will be calculated only if the highest bid price of the buy ALO is equal to or higher than the lowest ask price of the sell ALO.
  3. Indicative Equilibrium Volume (IEV) is the number of shares that could be matched at the IEP.
  4. Both IEP and IEV are continuously re-calculated and updated each time a new order is input during the Order Input Period of the Pre-Opening Session.

Detailed information on the Pre-opening Session can be found at HKEx Website.

Last Update: October 2020.