By Why Stocks Halt: Limit Up-Limit Down Bands
Why do stocks halt? Limit up-limit down bands pause trading for five minutes when price runs past a rolling reference. Here is the machinery, with data.
Stocks halt for five minutes under a rule called limit up-limit down: when the price runs past a band set around its own recent average, trading stops across every venue at once. Picture a small cap up 30 percent by mid morning. The quote stops updating, the last print stands, and a five minute clock starts. This page covers how those bands are built, how wide they are at each price, and what happens to a resting order while the tape is dark.
What you are seeing when a stock halts
A limit up-limit down pause is declared by the stock's primary listing exchange, and every other venue honors it at the same instant. For five minutes there are no executions anywhere. A broker screen may still show the last trade, which is now a stale number, or a quote with one side missing.
Two features mark this pause out from every other reason a ticker goes quiet. It is automatic, with no human deciding the stock needs a break, and it is fixed at five minutes by the plan itself. The tape carries a distinct halt code for a volatility pause, separate from the codes used for news and for market wide events.
Where the limit up-limit down rule came from
On May 6, 2010, prices across the US market fell and recovered inside a few minutes, and trades printed at levels nowhere near where the same names had been quoted moments before. Our 2010 flash crash breakdown walks through that afternoon. Single stock circuit breakers arrived within weeks, and the limit up-limit down plan replaced them in 2012, running as a pilot before it was made permanent in 2019.
What are limit up-limit down price bands?
The band is a percentage around a reference price, and that reference price is the average of eligible trade prices over the preceding five minutes, refreshed at least every 30 seconds. It rolls. This is the part most readers get wrong: the band is not measured from yesterday's close. A stock that climbs steadily all morning drags its own reference price up with it, and the band travels along underneath. A stock that jumps in one second finds the band still sitting near where it traded moments earlier. Quotes outside the band cannot be displayed or executed, so venues either reprice an aggressive limit order to the band edge or reject it.
How far does a stock actually travel in five minutes? The panel below measures every five minute window of the regular session over the trailing year for eight names, taking the full high to low excursion inside each window.
The exact SQL behind every number
SELECT
ticker,
round(quantileDeterministic(0.999)(range_pct, det), 2) AS p999_range_pct,
round(max(range_pct), 2) AS max_range_pct,
count() AS window_count
FROM
(
SELECT
ticker,
toStartOfFiveMinute(window_start) AS bucket,
toUnixTimestamp(toStartOfFiveMinute(window_start)) AS det,
(toFloat64(max(high)) - toFloat64(min(low)))
/ toFloat64(argMin(open, window_start)) * 100 AS range_pct
FROM global_markets.delayed_stocks_minute_aggs
WHERE ticker IN ('SPY', 'KO', 'AAPL', 'MSFT', 'NVDA', 'TSLA', 'COIN', 'MSTR')
AND window_start >= today() - 370
AND window_start < today() - 2
AND (toHour(toTimeZone(window_start, 'America/New_York')) * 60
+ toMinute(toTimeZone(window_start, 'America/New_York'))) >= 570
AND (toHour(toTimeZone(window_start, 'America/New_York')) * 60
+ toMinute(toTimeZone(window_start, 'America/New_York'))) < 960
GROUP BY ticker, bucket, det
HAVING min(low) > 0
)
GROUP BY ticker
ORDER BY max_range_pct DESCOver the trailing year, COIN posted the widest five minute excursion in the group at 6.4 percent of the price at the start of that window. Its 99.9th percentile window covered 3.1 percent, so even for the loudest name here, 999 windows in every 1000 stayed inside that figure. At the quiet end, AAPL never exceeded 2.15 percent across 19586 windows. A 5 percent band is nowhere near a typical five minutes. It is built for the outlier.
How wide is the limit up-limit down band?
Band width follows the security's tier and its price. The plan sorts every national market system stock into two tiers, and the percentage steps wider as the price falls:
- Tier 1, covering S&P 500 members, Russell 1000 members and a list of selected exchange traded products, priced above $3.00: 5 percent.
- Tier 2, meaning every other listed stock, priced above $3.00: 10 percent.
- Any stock priced from $0.75 to $3.00: 20 percent.
- Any stock priced below $0.75: the lesser of 75 percent or $0.15.
The tier lists and the exact schedule are amended from time to time by the exchanges that run the plan, so read the structure above as the shape of the rule rather than a permanent table. The mechanic is what stays put: a percentage of a rolling five minute average, wider for cheaper names. That same percentage buys a very different dollar cushion depending on where a stock trades.
The exact SQL behind every number
SELECT
ticker,
round(toFloat64(argMax(close, window_start)), 2) AS last_price,
round(toFloat64(argMax(close, window_start)) * 0.05, 2) AS band_5pct_dollars,
round(toFloat64(argMax(close, window_start)) * 0.10, 2) AS band_10pct_dollars
FROM global_markets.delayed_stocks_minute_aggs
WHERE ticker IN ('SPY', 'MSFT', 'AAPL', 'TSLA', 'NVDA', 'KO', 'PLTR', 'F')
AND window_start >= today() - 10
AND volume > 0
GROUP BY ticker
ORDER BY last_price DESCA 5 percent band on SPY near $767.96 gives $38.4 of room in either direction before the quote reaches the edge, and $76.8 inside the doubled windows described below. The same 5 percent on F near $13.96 is $0.7. One determined order covers that distance, which is why the percentages widen as prices fall.
Price zones matter more than they look, since a large share of the symbols on the tape trade at the cheap end.
The exact SQL behind every number
SELECT
price_zone,
stock_count,
round(stock_count * 100.0 / sum(stock_count) OVER (), 1) AS share_of_tape_pct
FROM
(
SELECT
multiIf(last_price < 0.75, 'under $0.75',
last_price < 3, '$0.75 to $3',
last_price < 20, '$3 to $20',
last_price < 100, '$20 to $100',
last_price < 500, '$100 to $500',
'$500 and up') AS price_zone,
count() AS stock_count
FROM
(
SELECT
ticker,
toFloat64(argMax(close, window_start)) AS last_price
FROM global_markets.delayed_stocks_minute_aggs
WHERE window_start >= today() - 8
AND window_start < today() - 1
AND volume > 0
GROUP BY ticker
HAVING last_price > 0
)
GROUP BY price_zone
)
ORDER BY multiIf(price_zone = 'under $0.75', 1,
price_zone = '$0.75 to $3', 2,
price_zone = '$3 to $20', 3,
price_zone = '$20 to $100', 4,
price_zone = '$100 to $500', 5,
6)Of the symbols that printed a trade in the last week, 728 last traded under $0.75 and 949 between $0.75 and $3.00, the two zones carrying the widest percentage bands. The $20 to $100 zone holds 50.4 percent of the list. The plan itself covers national market system securities, so the very cheapest corner of this population sits outside it. Cheap names get a wider band in percentage terms and a narrower one in cents, which is the trade the plan makes on purpose.
Why the bands double at the open and at the close
From 9:30 to 9:45 a.m. ET, and again from 3:35 p.m. to the 4:00 p.m. close, every band doubles. Tier 1 goes from 5 percent to 10, Tier 2 from 10 to 20. Those two windows carry the loudest price discovery of the day, and a band sized for midday would pause ordinary names every session.
The exact SQL behind every number
SELECT
formatDateTime(toStartOfInterval(toTimeZone(window_start, 'America/New_York'), INTERVAL 15 MINUTE), '%H:%i') AS et_time,
round(avg((toFloat64(high) - toFloat64(low)) / toFloat64(open) * 100), 3) AS avg_minute_range_pct,
round(quantileDeterministic(0.99)((toFloat64(high) - toFloat64(low)) / toFloat64(open) * 100,
toUnixTimestamp(window_start)), 3) AS p99_minute_range_pct
FROM global_markets.delayed_stocks_minute_aggs
WHERE ticker IN ('SPY', 'AAPL', 'MSFT', 'NVDA', 'TSLA')
AND window_start >= today() - 200
AND window_start < today() - 2
AND open > 0
AND (toHour(toTimeZone(window_start, 'America/New_York')) * 60
+ toMinute(toTimeZone(window_start, 'America/New_York'))) >= 570
AND (toHour(toTimeZone(window_start, 'America/New_York')) * 60
+ toMinute(toTimeZone(window_start, 'America/New_York'))) < 960
GROUP BY et_time
ORDER BY et_timeAcross five liquid names over the last several months, the average minute inside the 09:30 bucket covered 0.288 percent from high to low, against 0.087 percent in the 12:30 bucket. The final bucket of the day, 15:45, runs at 0.117 percent. The 99th percentile minute traces the same curve at a higher level, and the doubled bands sit over the two humps. Quoted spreads follow that daily shape too, covered in why spreads widen at the open.
Limit state, straddle state, and the fifteen second rule
A limit state begins when the best offer in the market sits exactly at the lower band without crossing the best bid, or the best bid sits exactly at the upper band without crossing the best offer. The price is pinned against the edge. Trading continues inside the band while this lasts, and the clock is what matters: if the quote does not step out of the limit state within 15 seconds, the listing exchange declares the five minute pause.
Most limit states never get that far. Liquidity arrives at the band edge, the quote steps back inside, and the fifteen seconds never elapse. That is how a name can spend a violent session touching its bands over and over with only one or two actual halts.
A straddle state is the other shape. The best bid sits below the lower band, or the best offer sits above the upper band, with the band range straddled by the quote rather than pinned at one edge. It appears when a related market is moving faster than the stock's own reference price can follow. A straddle state produces no automatic pause. The listing exchange may declare one if trading in that security is not occurring for 15 seconds.
How LULD differs from circuit breakers and news halts
Market wide circuit breakers watch one number, the S&P 500 against the prior day's close, and they stop everything at once. A Level 1 decline of 7 percent or a Level 2 decline of 13 percent halts all US equity trading for 15 minutes when it happens before 3:25 p.m. ET. A Level 3 decline of 20 percent ends the session at any hour. Those thresholds are index wide and rarely reached. Limit up-limit down is per stock and fires somewhere in the market on most days. Automated systems have to handle both kinds, which circuit breakers for trading bots walks through.
Regulatory halts are different again. On a Nasdaq listed name, the code T1 marks a halt with company news pending, and T12 marks a halt while the exchange requests additional information from the company. A person declares these, they last as long as the exchange requires rather than five minutes, and they often reopen a long way from the last print. Names that spend part of a week halted turn up regularly among the biggest stock movers this week.
What happens to your orders during a five minute pause
Nothing executes while the pause runs. Past that, behavior varies by venue and by order type, and a broker's own documentation is the place to confirm specifics.
- Resting limit orders generally stay in the book, though several exchanges cancel market orders and certain time sensitive types the moment a halt begins.
- New orders can usually be entered or cancelled during the pause, and they queue for the reopening.
- A limit order priced beyond the band cannot be displayed there. Venues slide it to the band edge or reject it.
- A stop order elects on a print, and no prints happen during a pause. When the reopening auction prints, an elected stop becomes a market order into whatever price that auction sets, which can land far from the stop price.
The reopening is an auction run by the primary listing exchange. Orders collect on both sides while the exchange publishes indicative prices, and a single crossing price prints the accumulated interest at once. The mechanics match the start of the day, covered in what is the opening auction. If the listing exchange cannot reopen within 10 minutes, other exchanges may resume trading in the name.
FAQ
Why do stocks halt for five minutes?
A five minute halt is the limit up-limit down volatility pause. When a stock's best bid or best offer sits at the edge of its price band for 15 straight seconds, the primary listing exchange stops trading for five minutes and then reopens with an auction.
How wide is the limit up-limit down band?
It is a percentage of a rolling five minute average price: 5 percent for large index member names above $3.00, 10 percent for other listed stocks above $3.00, 20 percent between $0.75 and $3.00, and the lesser of 75 percent or $0.15 below that. Each of those doubles during the first 15 minutes and the last 25 minutes of the session.
Can you buy or sell a stock while it is halted?
No trades execute during a halt. Most venues let you place or cancel orders while the pause runs, and those orders join the reopening auction, though some order types are cancelled automatically the moment the halt begins.
What is the difference between a trading halt and a circuit breaker?
A limit up-limit down halt applies to one stock and lasts five minutes. A market wide circuit breaker applies to every US equity at once and follows the S&P 500's decline from the prior close, at levels of 7, 13 and 20 percent.
Does a halt mean something is wrong with the company?
Not on its own. A volatility pause measures price movement over five minutes and nothing else. A regulatory halt, marked T1 or T12 on a Nasdaq listed name, is the different case: an exchange declares it around pending news or an information request.
Every panel here ships with the SQL that produced it, expandable under the chart. To see how close a name you follow has come to its own bands, ask the question in plain English on the Strasmore terminal.