What Is Limit Up-Limit Down (LULD)?
Limit Up-Limit Down (LULD) is the SEC-mandated single-stock circuit breaker introduced after the 2010 Flash Crash. It pauses trading in individual securities when the price moves rapidly outside a calculated price band (typically ±5-10% over a 5-minute window, varying by stock tier).
When a stock hits a LULD band, it enters a 'limit state' for 15 seconds; if it doesn't return inside the band, trading is halted for 5 minutes. The halt gives traders time to assess and reduces flash-crash cascade risk. After the halt, an auction reopens trading with a new price discovery process.
For active day traders, LULD halts are unpredictable disruptors — a profitable position can be locked during a halt and reopen at a worse price. Watch stocks approaching the ±5% band closely; on news-driven moves, multiple consecutive halts are possible. Most retail brokers display LULD status, though some only after a halt has already started.
Related terms
- Circuit Breaker — Automatic trading halt triggered by extreme price movement to give markets time to cool off.
- Trading Halt — Temporary suspension of trading due to news, volatility, or regulatory action.
- Limit Up / Limit Down — Maximum allowed price moves before trading is restricted to prevent excessive volatility.
- Gap Up — Price opening significantly higher than the prior close, leaving a 'gap' on the chart.