Stock Market Circuit Breakers Explained: Market-Wide Halts, LULD Bands and Single-Stock Pauses
Circuit breakers are the rules that stop trading when prices move too far, too fast. US stock markets have two main layers. Market-wide circuit breakers halt every stock and options exchange when the S&P 500 falls 7%, 13% or 20% in a day. Limit Up-Limit Down (LULD) bands work one stock at a time, pausing trading for five minutes when a single name breaks out of its allowed price range. On top of those sit ordinary trading halts that exchanges call for news, plus a short-sale restriction that kicks in after a 10% drop.
Most investors only notice these rules when they fire, usually on the worst day of a year. This page lays out how each mechanism works as of October 2026, the timing rules that trip people up, the history behind them, and the changes coming in December 2026 as US exchanges move toward overnight trading.
Market-wide circuit breakers: the 7%, 13% and 20% levels
Market-wide circuit breakers (MWCBs) are tied to the S&P 500. Each morning, three trigger levels are set from the index’s prior-day close:
| Level | S&P 500 decline | Before 3:25 p.m. ET | At or after 3:25 p.m. ET |
|---|---|---|---|
| Level 1 | 7% | 15-minute halt | No halt |
| Level 2 | 13% | 15-minute halt | No halt |
| Level 3 | 20% | Trading closed for the day | Trading closed for the day |
If the S&P 500 closed at 6,000, Level 1 would be 5,580, Level 2 would be 5,220 and Level 3 would be 4,800 the next session.
A few rules that matter in practice:
- Only declines count. There is no market-wide halt for a rally.
- Each of Level 1 and Level 2 can halt trading once per day. If the market reopens after a Level 1 halt and keeps falling, the next stop is Level 2, not another Level 1 pause.
- The 3:25 p.m. cutoff. A 7% or 13% drop late in the session doesn’t stop trading, because a 15-minute halt that close to 4:00 p.m. would wreck the closing auction. Only a 20% drop shuts the market late in the day.
- Regular hours only. The levels are monitored from 9:30 a.m. to 4:00 p.m. Eastern. A pre-market slump doesn’t trigger a halt, although the market can open straight into one.
- All US equity and options venues halt together. The primary listing exchanges then reopen stocks through auctions.
Starting December 6, 2026, exchange rules also spell out that after a Level 3 halt, trading won’t resume until 4:00 a.m. ET or later on the next trading day. Before the move to near-round-the-clock sessions, “closed for the rest of the day” needed no clarification. With overnight trading planned from 9:00 p.m. ET, the old wording could have been read as allowing trading to restart the same evening. Exchanges, including NYSE and the Cboe equity exchanges, filed matching rule changes in September 2026 to close that gap.
How the market-wide rules developed
The system was born out of the crash of October 19, 1987, when the Dow Jones Industrial Average fell 22.6% in one session. Regulators approved the first market-wide circuit breakers in October 1988. They were set in Dow points, with a one-hour halt for a 250-point fall and a two-hour halt for a 400-point fall.
Point-based triggers aged badly as the index rose. By October 27, 1997, the levels were 350 and 550 points. That afternoon the Dow fell 350 points, which triggered a 30-minute halt. After trading resumed it quickly fell through 550 points, and the exchanges closed for the day. The drop was around 7%, a bad day but nowhere near a crash, and shutting the market at that point drew heavy criticism. In 1998 the triggers switched to percentage drops in the Dow (10%, 20% and 30%).
The modern version came after the “flash crash” of May 6, 2010, when US stocks fell about 9% within minutes and then recovered, without any market-wide halt. In 2012 the SEC approved new rules that took effect in February 2013: the S&P 500 replaced the Dow as the benchmark, the levels dropped to 7%, 13% and 20%, halts were cut to 15 minutes, and the 3:25 p.m. cutoff was added. The rules ran as a pilot until the SEC made them permanent in March 2022.
The current system has fired four times, all at Level 1, all in March 2020 as COVID-19 hit markets: March 9, 12, 16 and 18. The first three came in the opening minutes; March 18 came during the session. An industry working group that reviewed the episode concluded the mechanism worked as designed. The closest call since was April 4, 2025, when the S&P 500 fell nearly 6% on the tariff selloff without reaching Level 1. As of October 2026, March 2020 remains the last market-wide halt.
Limit Up-Limit Down: price bands for single stocks
Market-wide halts are rare. Single-stock LULD pauses happen thousands of times a year. The LULD Plan, a national market system plan that all US equity exchanges and FINRA follow, replaced earlier single-stock circuit breakers starting in April 2013 and was made permanent in 2019.
The idea: every NMS stock (exchange-listed US equities and ETFs) gets a moving price band around a reference price, which is usually the average price of eligible trades over the previous five minutes. The reference price updates only when it moves 1% or more. The first reference price of the day is the opening price, or the opening quote midpoint if there is no opening trade.
Stocks are split into two tiers:
- Tier 1: S&P 500 and Russell 1000 stocks, plus certain high-volume ETPs.
- Tier 2: all other NMS stocks (rights and warrants excluded).
Band widths, during regular hours:
| Reference price | Tier 1 | Tier 2 |
|---|---|---|
| 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% |
The bands double during the last 25 minutes of trading (3:35 to 4:00 p.m.) for all Tier 1 stocks and for Tier 2 stocks priced at $3.00 or less. Tier 2 stocks above $3.00 keep their 10% band to the close. Until February 24, 2020, bands also doubled during the first 15 minutes of trading; Amendment 18 to the plan removed that opening widening.
A worked example: a Tier 1 stock with a $100 reference price can trade between $95 and $105 for most of the day, and between $90 and $110 after 3:35 p.m. A $50 Tier 2 stock has a range of $45 to $55 all day.
What happens when a stock hits its band
Hitting a band doesn’t stop trading straight away. The sequence is:
- Price band reached. Trades can’t print outside the band. Orders priced outside it are rejected or repriced.
- Limit state. If the best bid or offer sits exactly at the band (for example, the best offer equals the lower band in a selloff), the stock enters a limit state. Trading can continue at the band price.
- Trading pause. If the limit state doesn’t clear within 15 seconds, the primary listing exchange declares a five-minute trading pause across all venues. The halt code you’ll see on most platforms is LUDP.
- Reopening auction. The listing exchange reopens the stock with an auction. If the order imbalance is too large to reopen within the auction price collars, the pause is extended by five minutes, and the collar widens by another 5% in the direction of the move after each extension. After the first 10 minutes, the stock can reopen as soon as conditions allow.
- Late-day pauses. If a pause happens in the last 10 minutes of regular trading, the stock doesn’t reopen. The listing exchange runs its closing auction instead.
The pauses are frequent. The LULD Plan’s 2025 annual report counted 10,763 trading pauses in 2025, up 22.5% from 8,787 in 2024, out of 97,195 limit states. Most pauses fall on small, volatile Tier 2 names: biotech stocks after trial results, low-float IPOs, and stocks with heavy short interest. Squeeze candidates are regular visitors; see how short squeezes start for why.
Overnight bands from December 2026
US exchanges are preparing to extend trading to about 23 hours a day. LULD bands, however, have applied only from 9:30 a.m. to 4:00 p.m. That changes with Amendment 27 to the LULD Plan, filed May 27, 2026, approved by the SEC on August 5, 2026, and scheduled to take effect on December 6, 2026.
What Amendment 27 does:
- Adds overnight price bands from 9:00 p.m. to 4:00 a.m. ET, Sunday through Thursday nights.
- Sets the bands at 20% above and below a reference price. For leveraged ETPs, the 20% is multiplied by the fund’s leverage ratio.
- Uses two reference points: the official closing price and the last consolidated round-lot sale as of 7:45 p.m. ET, to account for after-hours trading.
- Requires trading centers to stop trades and quotes from printing outside the bands.
- Has no automatic five-minute pause overnight. Listing exchanges can still call regulatory halts.
The plan’s operators describe this as phase one, with a second phase to follow once there is data on how overnight trading behaves. The hours between 4:00 a.m. and 9:30 a.m., and between 4:00 p.m. and 9:00 p.m., still have no LULD bands.
Regulatory halts, volatility halts and the short-sale circuit breaker
LULD pauses and market-wide halts are volatility halts: automatic, rule-based and short. They are different from regulatory halts, which a listing exchange or the SEC calls on purpose.
| Type | Who calls it | Typical code | Usual length |
|---|---|---|---|
| News pending | Listing exchange | T1 | Until news is out and disseminated, often 30 to 60 minutes |
| News released, quotation resumption | Listing exchange | T2 | Short window before trading resumes |
| Additional information requested | Listing exchange | T12 | Can last days or longer |
| SEC trading suspension | SEC | H10 | Up to 10 trading days |
| LULD volatility pause | Listing exchange (automatic) | LUDP | 5 minutes, extendable |
| Market-wide circuit breaker | All exchanges (automatic) | Level 1, 2 or 3 | 15 minutes, or rest of day |
News halts protect investors from trading on information only some of them have, such as a merger, an FDA decision or a major legal ruling. A T12 halt is more worrying: it usually means the exchange has questions about the company or its disclosures. An SEC suspension usually signals concern about fraud, manipulation or a lack of current information, and stocks that come back from one often trade only over the counter.
There is also a circuit breaker for short sellers. Under SEC Rule 201 (the alternative uptick rule), when a stock falls 10% or more from the prior day’s close, short sales can only be executed above the current best bid for the rest of that day and the whole next day. It doesn’t stop trading. It stops short sellers from hitting bids during a slide. Traders call a stock in this state “SSR.”
What this means for orders and portfolios
For most long-term investors, circuit breakers mean one thing: on a very bad day, orders may sit unfilled for 15 minutes, or until the next session. Some practical points:
- Market orders during halts queue for the reopening auction, where the price can be far from the last trade. Limit orders give more control.
- Stop orders can trigger at the reopening price, not the stop price, after a gap through the level.
- Pauses don’t change the outcome. They slow the move so buyers can show up. On March 9, 2020, the S&P 500 still closed down about 7.6% after its morning halt.
- Leveraged ETFs feel these days most. A 7% index drop is roughly a 21% drop in a 3x fund before fees, and multiple halts in a volatile week compound the damage; see why leveraged ETFs decay.
- Margin matters more now. With the pattern day trader rule gone, brokers watch intraday exposure in real time; the new FINRA intraday margin standards explain how a halted, gapping position feeds into buying power.
Market-wide halts tend to arrive with signals you can already see: a spiking VIX, collapsing market breadth, and credit spreads blowing out. The main thing to watch next is December 6, 2026, when overnight LULD bands and the revised Level 3 rules go live together. Overnight sessions are thin, so the first real stress test will show whether 20% bands with no automatic pause are enough.