Limit Up-Limit Down (LULD)
Also called: LULD, Limit Up-Limit Down Plan, LUDP, volatility pause, price bands
The US market-wide rule that keeps individual stocks trading within percentage price bands around a recent average and pauses trading for five minutes if a band is not restored.
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How it works
Under the Limit Up-Limit Down Plan, each NMS stock has an upper and lower price band calculated from a reference price, generally the average price of trades over the preceding five minutes. Trades outside the band are not allowed. If the best quote sits at a band without trades occurring inside it, the stock enters a limit state. If the limit state is not resolved within 15 seconds, the primary listing exchange declares a five-minute trading pause (shown as LUDP on halt feeds), then reopens the stock with an auction.
Band widths
Bands depend on the stock's tier and price:
| Reference price | Tier 1 (S&P 500, Russell 1000, some ETPs) | Tier 2 (other NMS stocks) |
|---|---|---|
| Above $3.00 | 5% | 10% |
| $0.75 to $3.00 | 20% | 20% |
| Below $0.75 | lesser of $0.15 or 75% | lesser of $0.15 or 75% |
Bands are doubled during parts of the opening and closing periods for some securities; the exact schedule is set by the Plan.
Worked example
Hypothetical: Company X is a Tier 2 stock with a five-minute average price of $5.00. Its bands are $4.50 and $5.50. If buyers push the quote to $5.50 and no trades print inside the band for 15 seconds, trading pauses for five minutes. If Company X were priced at $2.00, its bands would be 20% wide: $1.60 to $2.40.
Why it matters
Fast-moving small caps can be paused several times in one session. Each pause interrupts trading and ends with a reopening auction, which can print well away from the last trade. The reference price moves continuously, so the band follows the stock as it rises or falls.
How to spot it
LULD pauses appear on exchange halt feeds with code LUDP and in the Signal8 halts screener. The full Plan text is published by the LULD Plan participants. See Trading halts.
Related terms
Guides that use this term
Trading mechanics · 6 min read
Trading Halts Explained: Halt Codes, LULD Pauses and How Trading Resumes
What T1, T2, T12, H10, LUDP, LUDS and M halt codes mean, how Limit Up-Limit Down price bands work, and how a halted stock reopens.
Trading mechanics · 5 min read
Premarket Trading and Relative Volume (RVOL): How Early Volume Is Measured
How the 4:00 to 9:30 a.m. ET premarket session works, how relative volume is calculated, and why the baseline behind an RVOL figure matters.
Research pages · 5 min read
Signal8's Premarket Scanner: What Every Column Means
A column-by-column guide to Signal8's scanner in the premarket session, from Gap % and RVOL to float, short interest, squeeze score and catalysts.
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Signal8 Screeners: Movers, Halts, Dilution, Must-Raise and Delisting
What each board in Signal8's screeners hub lists, how its columns and presets work, how often it refreshes, and which boards need an account or Pro.