LULD halt (limit up-limit down)
A LULD halt is a five-minute trading pause under the Limit Up-Limit Down plan, called when a stock reaches the edge of its price band and stays there for 15 seconds. The bands sit a set percentage above and below the stock's average price over the last five minutes, to stop sudden, extreme moves in US stocks.
Why it matters to a small-cap momentum trader
Low-float momentum stocks reach their bands far more often than large caps, so pauses are part of trading them. A stock that pauses at its upper band, limit up, often reopens higher, but not always, and you cannot get out while it is paused. Knowing roughly where the next band sits tells you how far a stock can run before it pauses, and where a stop may not fill. During the pause market orders do not fill, nothing prints on the tape, and the reopening auction sets the next price.
The rule
Reference price. The average price of eligible trades over the preceding five minutes. Band edges are rounded to the nearest penny, and bands apply only in regular hours, 9:30 a.m. to 4:00 p.m. ET.
Tiers. Tier 1 is the S&P 500, the Russell 1000 and some exchange-traded products. Tier 2 is every other listed stock, except rights and warrants, which have no bands. Almost every small cap is Tier 2.
Band width. Picked from the previous day's closing price and fixed for the whole day:
| Previous close | Tier 1 | Tier 2 |
|---|---|---|
| Above 3 dollars | 5% | 10% |
| 75 cents to 3 dollars | 20% | 20% |
| Below 75 cents | 15 cents or 75%, whichever is less | 15 cents or 75%, whichever is less |
Limit state and pause. When the best offer sits at the lower band, or the best bid at the upper band, the stock is in a limit state and its bands stop moving. If it does not leave the limit state within 15 seconds, the listing exchange pauses trading for five minutes and reopens the stock with an auction. The pause runs longer if the auction cannot open.
Because the width comes from the previous close, a stock that closed under 75 cents keeps its 15-cent band all day, even after it runs past 3 dollars.
The rule depends on the date: Amendment 18
The band has doubled near the open and the close, and which windows double changed on 24 February 2020, when Amendment 18 to the LULD plan took effect.
- Before 24 February 2020: the band doubled for every stock in the first 15 minutes, 9:30 to 9:45 a.m. ET, and the last 25 minutes, 3:35 to 4:00 p.m. ET.
- From 24 February 2020: no opening doubling. The closing doubling, 3:35 to 4:00 p.m. ET, applies only to Tier 1 stocks and to Tier 2 stocks whose previous close was 3 dollars or less. A Tier 2 stock that closed above 3 dollars keeps its 10% band all day. On a half-day, the closing window is the last 25 minutes before the 1:00 p.m. close.
LULD in Hindsight Markets
Bands are worked out from that day's trades by the plan's formula, under the rules in force on the date you replay, and no fill goes through a band. The pauses are the ones that really happened that day, from the exchanges' own halt messages. The Level 2 picture on the home page is MEDS paused at 10:48 ET on 2026-09-16: no prints on the tape while the book kept streaming.
Practice this on a real past day in Hindsight Markets
Replay a morning when a small cap ran into its bands, watch the pause and the reopen in real time, and see where your orders would have filled.