Nasdaq Trading Halt Rules
(10) A trading pause initiated pursuant to Rule 4120(a)(12) ends when Nasdaq releases the security for trading. For these Nasdaq-listed securities, there will be a 5-minute “initial display period only” prior to the end of the break, during which market participants will be able to enter quotes and orders in that security into Nasdaq systems. If you are in a stock that is stopped, the most important thing is not to panic. Volatility stops after 5 minutes. However, compliance messages or shutdowns can be more intimidating situations. (i) For the purposes of this rule, a market decline means a decrease in the price of the S&P 500 Index between 9:30 a.m. EST and 4:00 p.m. EST on a trading day relative to the closing price of the S&P 500®® Index for the previous trading day. Level 1, 2 and 3 market declines applicable to the trading day will be released by 9:30 a.m. EST. (ii) If the primary listing market ceases trading in all shares, the Exchange will cease trading in such shares until trading has resumed on the primary listing market or notice has been received from the primary listing market indicating that trading may resume. If the primary listing market does not reopen a security within 15 minutes of the expiry of the 15-minute holding period, the exchange may resume trading in that security.
(11) must suspend trading between 9:45 a.m. and 3:35 p.m. or, in the case of an early closing price, 25 minutes before the close of trading, in a security listed on the Nasdaq that is not covered by the Limit Up-Limit Down plan, excluding rights and warrants, immediately for 5 minutes if the price of this security fluctuates by a percentage specified below within a period of 5 minutes. The two reasons above are “regulatory” trading stops and are implemented on many major exchanges (e.g., NYSE American, NASDAQ, and New York Stock Exchange). If a U.S. exchange issues a regulatory stop on a security, other U.S. exchanges that also trade the security will comply with the shutdown.  Trading delays often occur at the beginning of the trading day when the market is open. Typically, businesses make important announcements when the market is closed between 4 p.m. and 9:30 a.m. Eastern Time. This window gives investors time to assess the importance of the news and place orders at the prices they deem appropriate.
In some cases, this reaction by the investor can lead to an imbalance between buy and sell orders at the opening of the next trading day. In this case, an exchange may delay the opening of trading in a particular stock so that orders can be received to correct the imbalance. Volatility stops are single stock circuit breaker stops that trigger 5-minute stops during rapid price spikes or drops that exceed the acceptable trading price range (ATPR) for 15 seconds. The ATPR is calculated as the average price of the previous 5-minute trading period. (i) If a decline in the Level 1 or Class 2 market occurs after 9:30 a.m. EST and up to and including 3:25 p.m., or in the case of an early close scheduled for 12:25 p.m. EST, the Exchange will suspend trading in all shares for 15 minutes following a decline in the Tier 1 or Class 2 market. The exchange stops trading based on a drop in the Tier 1 or 2 market only once per trading day. The Exchange will not cease operations if a decline in the Level 1 or Level 2 market occurs after 3:25 p.m. EST or in the case of an early closing price at 12:25 p.m.
EST. (a) In the event of a break caused by a limit reduction, the lower price of the auction collar shall be obtained by subtracting 5 % of the reference price of the auction, rounded to the nearest minimum increase, or, in the case of securities with a reference auction price of USD 3 or less, USD 0,15 from the reference price of the auction, and the higher price of the auction collar is the price of the upper range on the LURD fluctuation band; that existed at the time the commercial pause was triggered. ¢ Size. All additional orders must be entered with a size of one or more normal trading units. If an additional order is reduced to less than a normal trading unit, the rest of the additional order will be automatically cancelled. (A) If an applicable required value is still not calculated or widely disseminated after the close of the normal trading session, Nasdaq may only trade the derivative proceeds in the post-trade session if the listed market has traded the derivatives proceeds continuously until the end of its normal trading session. (4) (A) If Nasdaq determines that there is a basis under Rule 4120(a) to initiate a trading stop, the start of the trading stop will take effect on the date specified by Nasdaq in a notice on a publicly available Nasdaq website.