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Stocks, ETFs, and Equities Macro · T+1 Settlement and Equity Mechanics

LULD: per-stock guardrails

Explain Limit Up Limit Down bands and how single-stock halts work.

3 min read+25 XPLesson 15 of 55
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Stocks, ETFs, and Equities Macro

T+1 Settlement and Equity Mechanics

Lesson 15 of 5527%
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Lesson 15 of 55Stocks, ETFs, and Equities MacroT+1 Settlement and Equity Mechanics

Today's tiny win: make one idea click.

Explain Limit Up Limit Down bands and how single-stock halts work.

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When a single stock gets the timeout

Market-wide circuit breakers handle index-level crashes. Limit Up Limit Down — LULD — handles individual stocks. The rules were rolled out in 2012-2013 after the 2010 Flash Crash, where a few thinly traded names went haywire and dragged the whole index sideways for a few minutes. LULD puts a price band around every stock and pauses trading if price moves outside it.

Wick points at a chalkboard showing a $50 stock with a 5% band and a pause near $47.50, teaching how a LULD band is worked out.LULD band exampleBig stock at $505% bandPause near $47.50
Wick saysAn S&P 500 stock at $50 has a 5% band, so a drop near $47.50 pauses it.

How wide is the band? It depends on two things: how liquid the stock is and what time of day it is. Tier 1 stocks (S&P 500, Russell 1000, major ETFs) priced above $3 get 5% bands. Tier 2 stocks above $3 get 10% bands. Sub-$3 names get 20% bands or 15 cents, whichever is larger. During the first 15 minutes after open and the last 25 minutes before close, all bands double — because those windows naturally see bigger moves.

Here is what happens in practice. A biotech is sitting at $20. News drops about a failed clinical trial. Sellers pile in. Price falls to $19, $18, $17 — but $17 is the lower LULD band based on the 5-minute reference price. Trading pauses for 5 minutes. The exchange auctions a reopen price. That auction might print at $15, or $14, or wherever the imbalance settles. Continuous trading then resumes with new bands around the new reference price.

Wick reads a headline that a biotech trial failed while the practice chart drops, teaching that a stock piercing its band pauses and then reopens, often with a gap.MARKET NEWSBiotech trialfailsPractice chart?
Wick saysBad news can push a stock through its band. It pauses 5 minutes, then reopens by auction.

If you are holding the stock during an LULD halt, your existing stops queue until reopen — same rule as market-wide halts. Limit orders also queue. The reopen auction can print far from where the halt started, especially on news. Treat any single-stock halt the same way you treat circuit breakers: respect the pause, expect a gap on reopen.

Wick shows a clock with 2x bands arcs at the open and close and a Normal arc between, teaching when LULD bands get wider.24612182x bandsNormal2x bandsHours in ET
Wick saysBands double in the first 15 minutes and the last 25 minutes, when moves are bigger.

Recap: LULD bands around every stock — 5%, 10%, or 20% based on tier and price. Doubled at open and close. Piercing triggers a 5-minute halt and reopening auction. Stops queue and reopens often gap.

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0 / 2 answered

1. An S&P 500 stock at $50 sees its 5-minute reference price set at $50. What is the lower LULD band during regular trading hours (not open/close)?

2. Why are LULD bands wider during the first 15 minutes after open and last 25 before close?

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