What are Trading Halts and Delays?
Securities exchanges, such as the New York Stock Exchange (NYSE) and American Stock Exchange (Amex), as well as the Nasdaq Stock Market, have the authority to halt and delay trading in a security. A trading halt-which typically lasts less than an hour but can be longer-is called during the trading day to allow a company to announce important news or where there is a significant order imbalance between buyers and sellers in a security. A trading delay (or "delayed opening") is called if either of these situations occurs at the beginning of the trading day.
There are two types of trading halts and delays - regulatory and nonregulatory. The most common regulatory halt and delay happen when a company has pending news that may affect the security's price (a "news pending" halt or delay). By halting or delaying trading, market participants can have time to assess the impact of the news. Another type of regulatory halt happens when a market halts trading in a security when there is uncertainty over whether the security continues to meet the market's listing standards. When a regulatory halt or delay is imposed by a security's primary market, the other U.S. markets that also trade the security honor this halt.
Nonregulatory halts or delays occur on exchanges, such as the NYSE and Amex (but not on Nasdaq), when there is a significant imbalance in the pending buy and sell orders in a security. When an imbalance occurs, trading is stopped to alert market participants to the situation and to allow the exchange specialists to disseminate information to investors concerning a price range where trading may begin again on this exchange. A nonregulatory trading halt or delay on one exchange does not preclude other markets from trading this security.
You can find out what stocks have had their trading halted on the NYSE, Amex, and the Nasdaq Stock Market, as well as on the OTC Bulletin Board.
The SEC does not halt or delay trading in a security for news pending or order imbalances, but it can suspend trading for up to ten days and, if appropriate, take action to revoke a security's registration.From the U.S. Securities and Exchange Commission website.