Trading Halts and Circuit Breakers

A trading halt is a temporary pause in trading. It can affect a single stock, while important news is released or when the price moves too fast, or an entire market during an extreme fall. Halts exist to give everyone time to absorb information and to stop disorderly, panic driven trading. For traders, they matter because you cannot buy or sell during a halt, and prices can reopen far from where they stopped.

Why single stocks are halted#

• News pending: an exchange may halt a stock just before or during major announcements, such as a merger or regulatory decision, so that all investors see the news at the same time.
• Volatility pauses: under the US Limit Up Limit Down (LULD) mechanism, a stock that moves outside a price band around its recent average must pause for at least five minutes.
• Regulatory concerns: the SEC can suspend trading in a security for up to ten days, for example over questions about accurate information.
• Listing issues: failure to file reports or meet listing standards can lead to halts and delisting.

Limit Up Limit Down bands#

LULD sets a band above and below a reference price, roughly the average price over the previous five minutes. The width depends on the stock's price and category; for many large stocks during most of the day, it is 5%. If trading would happen outside the band, the stock enters a limit state for 15 seconds; if prices do not return inside the band, trading pauses for five minutes and then reopens with an auction. This system was introduced after the May 2010 Flash Crash. See The 2010 Flash Crash.

Market wide circuit breakers#

If the whole US stock market falls sharply, trading in all stocks halts. The trigger is the S&P 500's decline from the previous day's close:

After 3:25 p.m., Level 1 and 2 declines do not trigger a halt; a Level 3 decline at any time ends trading for the day. Level 1 was triggered four times in March 2020, during the COVID-19 crash. See The COVID-19 Crash.

These rules were introduced after the crash of October 1987, when the Dow Jones fell about 22.6% in a single day. See Black Monday 1987.

Other markets#

• Futures have price limits that restrict how far prices can move in a session, with different rules overnight and during the day.
• Other countries' stock exchanges have their own circuit breakers and volatility interruptions.
• Crypto markets have no market wide circuit breakers. Individual exchanges may pause trading during technical problems, but prices keep moving elsewhere.

What halts mean for traders#

1. You cannot exit during a halt. Your stop orders cannot fill while trading is paused.
2. The reopening price can gap. After news, a stock can reopen far above or below the halt price.
3. Order handling varies. Some brokers cancel or hold orders during halts. Know your broker's rules.
4. Options and related products may halt too, and their prices can be hard to judge while the stock is paused.
5. Halts often happen in volatile small caps, where a series of LULD pauses can occur in one day.

This is one reason Position Sizing matters more than stop placement for event risk: the stop cannot protect you from prices that are never traded.

Frequently asked questions#

Why do stocks get halted?#

Usually for pending news, extreme price moves under volatility rules, or regulatory concerns about the company's information or listing status.

How long does a trading halt last?#

Volatility pauses typically last five minutes. News halts can last minutes to hours. Regulatory suspensions can last up to ten days.

What happens to my orders during a halt?#

They generally cannot be executed while trading is paused. Depending on your broker, they may stay open, be cancelled or be held until trading resumes.

Sources#

• U.S. Securities and Exchange Commission, Market wide circuit breakers
• Wikipedia, Trading curb