Reverse splits, listing and halts
Trading Halts Explained: Halt Codes and LULD Pauses
What trading halt codes T1, T2, T12, H10, LUDP and M mean, how Limit Up-Limit Down price bands trigger pauses, and how a halted stock reopens for trading.
What is a trading halt?
A trading halt is a stop on trading in one security, called by the exchange where it is listed (or, in the case of a suspension, by the SEC). While a stock is halted, no trades in it can print on any US venue. Orders can usually still be entered or cancelled, but nothing executes until the halt lifts.
Halts come in two broad families. Regulatory halts pause trading around information: news is pending, the exchange wants more information from the company, or the SEC has suspended the stock. Volatility pauses are mechanical: under the Limit Up-Limit Down plan, a stock that moves too far, too fast within a short window is paused for five minutes. Each halt carries a short reason code, and knowing what the code means tells you which kind of stop you are looking at. The live list of halts in effect right now is the trading halt scanner, and why stocks get halted explains how to read it.
The halt codes you will see most
Nasdaq publishes the code list on its Nasdaq Trader site, and the same codes appear in most market data feeds. These are the common ones:
| Code | Name | What it means |
|---|---|---|
| T1 | News pending | The exchange halted trading because the company is about to release material news. |
| T2 | News released | The news has begun dissemination; trading remains halted while it spreads. |
| T12 | Additional information requested | The exchange has asked the company for more information and is waiting for it. |
| H10 | SEC trading suspension | The SEC has suspended trading in the security. |
| LUDP | Volatility trading pause | A Limit Up-Limit Down pause in a Nasdaq-listed security. |
| LUDS | Volatility pause, straddle condition | A pause called while the quote straddles a price band, without a formal limit state. |
| M | Volatility trading pause | A pause in a security listed on another exchange, as shown in Nasdaq's feed. |
A T1 halt is often followed by a T2 on the same stock: first the stop while news is pending, then a period after release so the information can reach the market before trading reopens. Other codes you may run into include H4 (non-compliance with listing requirements), H9 (not current in required filings) and MWC1 to MWC3 (market-wide circuit breaker halts that stop all stocks at once).
How Limit Up-Limit Down works
The Limit Up-Limit Down (LULD) plan, approved by the SEC in 2012, places a price band around every listed stock during regular trading hours (9:30 a.m. to 4:00 p.m. ET). The band is centered on a reference price, which is the average price of eligible trades over the previous five minutes.
The width of the band depends on the stock's tier and its prior closing price:
| Prior close | Tier 1 (S&P 500, Russell 1000, some ETPs) | Tier 2 (everything else) |
|---|---|---|
| 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% |
Under the plan text, these percentages are doubled between 9:30 and 9:45 a.m. ET and between 3:35 and 4:00 p.m. ET. Rights and warrants are excluded.
When the best bid or offer touches a band and stays there, the stock enters a limit state. If the limit state does not clear within 15 seconds, the listing exchange declares a five-minute trading pause. That pause is what shows up as LUDP (or M for a non-Nasdaq listing).
A worked example
Take a hypothetical Tier 2 stock, Company X, that closed yesterday at $4.00. At 11:00 a.m. its five-minute average trade price is $5.00.
- Band percentage: 10% (Tier 2, prior close above $3.00).
- Lower band: $5.00 × (1 − 0.10) = $4.50.
- Upper band: $5.00 × (1 + 0.10) = $5.50.
If the best bid rises to $5.50 and the market cannot trade through the limit state within 15 seconds, a five-minute pause begins. Had the same move happened at 9:35 a.m., the band would have been 20% wide, from $4.00 to $6.00.
How trading resumes
A halt ends with a reopening, not with trading simply switching back on.
- After a volatility pause, the listing exchange attempts to reopen the stock about five minutes later with an auction that matches buy and sell interest at a single price. If there is a large imbalance between buyers and sellers, the pause can be extended. If the reopening happens more than ten minutes after the pause began, the plan applies triple-width bands for the first 30 seconds afterward.
- After a news halt (T1 then T2), the exchange typically publishes a quotation-only period before the resumption time, and then reopens with an auction.
- After a T12 or H10, there is no fixed clock. A T12 lasts until the exchange is satisfied; an SEC suspension under Section 12(k) of the Exchange Act can last up to ten trading days.
The reopening price can be far from the last trade before the halt, because it reflects everything that happened while trading was stopped. One halt can also lead to another: a stock that reopens and moves sharply again can be paused again under the same LULD rules.
Halts outside the exchange
OTC securities are not listed on an exchange, so LULD does not apply to them. FINRA can halt OTC trading under its own rules, and those halts appear on FINRA's OTC daily list rather than in an exchange's halt feed. The SEC can also suspend trading in any security, listed or OTC.
How to check a halt on Signal8
- The Halted scanner lists stocks halted right now, most recent first. An empty list is a normal state: it means no active halts were reported at that moment.
- During regular hours, Halt Resumers lists stocks that resumed in the last 15 minutes, and LULD Runners lists stocks with two or more volatility halts today.
- The news feed and the live SEC filings feed are where the announcement behind a T1 or T12 halt usually surfaces.
- In the Terminal, open a symbol to see its quote, chart and filings in one workspace.
Live screen
Active trading halts
Related reading: how premarket volume is measured, what a reverse split does, and how a bankruptcy case unfolds.
FAQ
What is the difference between a T1 and a T2 halt?
A T1 halt means news is pending: the exchange has stopped trading because the company is about to release material information. A T2 means the news has started to be disseminated through a Regulation FD compliant method, but trading is still halted so the information can reach the market. The two often appear in sequence on the same stock, followed by a quotation period and a reopening auction.
How long does a LULD trading pause last?
A Limit Up-Limit Down pause is five minutes. At the end of that time the listing exchange tries to reopen the stock with an auction. If there is a significant imbalance between buy and sell orders, the reopening can be delayed and the pause extended. A new pause can also start later if the stock hits a band again after reopening.
Can a stock be halted before the market opens?
Regulatory halts such as T1, T12 or H10 can be called at any time, including before the open. LULD volatility pauses cannot, because the price bands only apply during regular trading hours from 9:30 a.m. to 4:00 p.m. ET. A stock can therefore move a long way in the premarket session without a volatility pause.
Does a T12 halt mean something bad happened?
Not necessarily. T12 means the exchange has requested additional information from the company and is waiting to receive it. It can relate to unusual trading, a corporate announcement, or a listing question. The code itself does not say which, and the reason often only becomes clear from a later press release or SEC filing.
See it on DilutionScan
Companies DilutionScan covers, with the instruments read from their SEC filings. Open one to see each instrument and the filing it came from.
- GNSGenius Group Limited8 warrant series, 1 convertible, 1 ATM program, 3 shelf registrations and 2 completed offerings on file
- SMXSMX (Security Matters) Public Limited Company Ordinary Shares10 warrant series, 8 convertibles, 2 equity lines, 4 shelf registrations, 4 S-1 registrations and 2 completed offerings on file
- MLGOMicroAlgo, Inc. Ordinary Shares2 warrant series, 5 convertibles and 2 shelf registrations on file
- HOLOMicroCloud Hologram Inc. Ordinary Shares2 warrant series, 1 convertible, 3 shelf registrations and 2 completed offerings on file
Terms in this guide
- Trading halt
- A trading halt is a temporary stop in trading of a security ordered by its listing exchange or the SEC, for example pending material news, to request information, or after a volatility pause.
- Limit Up-Limit Down (LULD)
- Limit Up-Limit Down (LULD) is the US market-wide rule that keeps each stock trading within price bands around a recent average and pauses trading for five minutes if a band is not restored.
- Form 8-K
- A Form 8-K is the SEC current report a public company files, generally within four business days, to disclose material events such as agreements, offerings, executive changes and listing notices.
Related guides
- Reverse Stock Split Explained: How It WorksHow a reverse stock split works, its stages and filings, fractional shares, ADS ratio changes, bid-price rules and Nasdaq's 250-to-1 cap.
- Relative Volume (RVOL) and Premarket Trading ExplainedHow relative volume (RVOL) is calculated, how the 4:00 to 9:30 a.m. ET premarket session works, and why the baseline behind an RVOL figure changes the reading.
- Chapter 11 vs Chapter 7: Bankruptcy Stages for StocksChapter 11 vs Chapter 7 bankruptcy for public companies: each stage from petition and DIP financing to emergence, 8-K Item 1.03, and why tickers gain a Q.
- 8-K Item Codes Explained: Items 1.01 to 9.018-K item codes explained: what Items 1.01, 2.03, 3.01, 3.02, 5.02 and 9.01 mean, the four-business-day rule, and the item combinations that flag a financing.
- How to Trade Penny Stocks Without Getting DilutedA dilution-first guide to penny stocks. How new shares reach the tape, which SEC filings announce them, worked examples, and a 20-minute filing check.
- The Reverse Split Dilution Cycle ExplainedHow reverse splits, resale registrations and convertible financings can repeat as a dilution cycle, with a typical timeline and a worked two-loop share count.
Check any ticker for dilution
DilutionScan reads each covered company's SEC filings and lists its warrants, convertibles, ATM programs, shelves and S-1s on one page, with a dilution rating and cash runway.
This guide is from the Signal8 Academy, the research team behind DilutionScan. Educational content only. DilutionScan and Signal8 are not broker-dealers or investment advisers, and nothing here is a recommendation to buy or sell any security.