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Extraordinary Order Book Situations

Should an extraordinary situation arise, the Exchange, as a part of its market steering activities, may take all measures it deems necessary to preserve the fairest and most orderly trading possible. Further information in this regard can be found in the Rule Book[pdf] and Directive 3: Trading[pdf].

Intervention in the opening of trading

The Exchange may delay the opening of trading by a predefined amount of time if a number of criteria are met.

  • Delay Open
    If the theoretical opening price deviates sharply from the reference price, a Stop Trading condition is automatically triggered and the opening is delayed by 5 or 15 minutes. The limits for deviation and the length of time for which trading is stopped are set out in the Trading Guide.
  • Delayed Opening "No Quote"
    If at the opening there are no quotes on the order book even though executable orders exist on both sides of the market, the opening is automatically delayed. Trading in the affected securities will be postponed. The Exchange specifies the length of the delay (Stop Trading Duration) in advance.

Trading interruptions

The Exchange may intervene in continuous trading by halting trading in a security for a specified period of time. This can happen for different reasons.

  • Non Opening
    The Exchange will not open trading in a given security as long as long as the auction procedure does not result in the execution of all unlimited orders on the book (Non Opening). In this status, it is also not possible to calculate a theoretical opening price (TOP).

    The order book remains open and the opening procedure is restarted with each change in the order book. The Non Opening condition lasts until all unlimited orders can be executed.
  • Stop Trading
    The Stop Trading condition depends on the probable next paid price for a security. If this deviates by n% or more from the reference price, the Exchange halts trading in this security for 5 or 15 minutes. The security will be revalued for reopening or go into Non Opening status.
  • Stop Trading "No Quote"
    If there are no quotes in the order book even though executable orders exist on both sides of the market, the Exchange imposes a Stop Trading condition for a predefined period of time (Stop Time Duration).
  • Avalanche Stop Trading
    The criteria for an Avalanche Stop Trading condition relate to a predefined period of time (Avalanche Time) and a predefined price range (Stop Trading Range). If the next trade during this period of time would potentially deviate from the reference price by an amount that is higher than the predefined price range, the trade is not executed. The Exchange halts trading in the security concerned for a predefined period of time (Stop Time Duration).


In extraordinary circumstances, the Exchange may also temporarily suspend trading in a security. The duration of the suspension is decided on a case-by-case basis and should be as short as possible. In the event of a suspension of trading, participants and the Exchange must consider various aspects.

  • The issuer that submitted the original listing application for the security in question may apply to the Exchange for a suspension in trading. Where possible, this should take place at least 90 minutes before the opening of trading.
  • When assessing the imposition and duration of a suspension, the Exchange must weigh a number of interests. The public interest lies in having an open, transparent market and continuous pricing. On the other hand, there is the interest of ensuring that all participants are treated equally with regard to price-sensitive information.
  • In the case of securities with a secondary listing and any related derivatives, the Exchange also takes into account the decisions of the other major trading exchanges.
  • Moreover, in terms of equity securities with a secondary listing, the Exchange also takes into account the decisions of the other major trading exchanges.