Trading Halts Explained

Exchanges occasionally stop trading altogether, not to hide bad news, but to give the market a moment to reset when prices move faster than information can be absorbed.

Why exchanges pause trading at all

A trading halt is a temporary stop in trading for a single security or, in extreme cases, the entire market. The purpose is almost always the same: to slow things down when price moves are happening faster than the market can reasonably process the information behind them. Halts give traders a pause to reassess, prevent panic-driven cascades from feeding on themselves, and in some cases wait for material news to be properly disseminated before trading resumes on a level playing field.

Circuit breakers and market-wide halts

Market-wide circuit breakers are triggered when a major index, typically the S&P 500, falls by a set percentage in a single session. In US markets, a 7% decline triggers a 15-minute halt, a 13% decline triggers another 15-minute halt, and a 20% decline halts trading for the rest of the day. These thresholds exist specifically to interrupt the kind of self-reinforcing selling that can spiral when automated systems and panicked investors are all hitting sell at once.

Volatility halts and Limit Up-Limit Down

Individual stocks can also be halted through the Limit Up-Limit Down mechanism, which pauses trading in a single security when its price moves outside a defined percentage band relative to recent trading, typically for five minutes. This is separate from market-wide circuit breakers and happens far more often, usually in lower-liquidity or news-driven stocks where a burst of orders can otherwise send the price to an extreme level in seconds.

News-pending halts and historical examples

Exchanges can also halt a specific stock ahead of a major, market-moving announcement, a pending merger, an FDA decision, or a significant corporate disclosure, to ensure the news is public before trading resumes, rather than letting a handful of informed traders react first. These halts are common around scheduled announcements and typically last until the company confirms the news has been released. Historically, notable halts have marked some of the most stressful days in market history, including the market-wide circuit breakers triggered repeatedly in March 2020 as COVID-19 fears spread, and the Limit Up-Limit Down mechanism, introduced after the 2010 Flash Crash specifically to prevent single stocks from trading at extreme, momentarily illiquid prices. Each of these mechanisms exists because a full, uninterrupted trading halt is sometimes safer for everyone involved than letting the market keep moving on incomplete or lopsided information.