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Market Structure
What Is LULD (Limit Up-Limit Down)?
LULD is the guardrail that stops a single stock from flash-crashing or spiking on a bad print — a 5-minute timeout when price gets disorderly.
NoVo Options Trading · 2026
Educational only, not financial advice. Market rules and thresholds can change — verify current specifics with the exchanges or your broker.
LULD (Limit Up-Limit Down) pauses trading in a stock for ~5 minutes when its price moves too far, too fast outside a set price band. It’s a single-stock circuit breaker designed to prevent disorderly moves.
How LULD works
Each stock has a price band around a reference price — roughly 5–10% for higher-priced (Tier 1) names and wider for others — recalculated continuously. If price would trade outside the band and doesn’t re-enter within a short window, a 5-minute halt triggers. Trading then reopens via an auction. It stops erroneous prints and flash-crash-style cascades in a single name.
Why it exists
LULD was introduced after the 2010 “flash crash” to prevent individual securities from trading at absurd prices during momentary dislocations. It keeps a single stock’s moves orderly without halting the whole market (that’s the job of the broader circuit breakers).
LULD is a per-stock speed limit: move too far too fast, and the stock takes a 5-minute timeout to re-find fair value.
What it means for a scalper
For ultra-liquid SPY, LULD halts are very rare — but if you trade individual stocks (or on a genuine crash day), they matter: a halt freezes you and the reopen can gap. It’s the single-stock cousin of the limit up/limit down concept and part of the market’s volatility guardrails.
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NoVo is a software tool for market analysis and for executing trades you initiate, not financial advice. This article is general education, not investment advice. Options trading involves substantial risk of loss, up to and including your entire capital. NoVo makes no guarantee of profit, win rate, or performance, and past results do not predict future outcomes. You are responsible for your own broker account, configuration, and trading decisions.