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Key Takeaways
- A halt can affect one listing, one venue, a group of securities, or the entire market depending on its cause.
- Common reasons include material news, extraordinary volatility, regulatory concerns, listing issues, and system problems.
- Nothing executes in the halted scope; ask the broker whether your open orders stay queued, can be canceled or join the reopening auction.
- Exchange news and volatility halts resume through a quotation period and a reopening auction before continuous trading starts.
- The reopening price can gap sharply because information and orders accumulate while executions are paused.
What is a trading halt?
A trading halt is a temporary interruption of quoting or trading in a security, venue or market, and its halt code tells you why and how wide. Common causes include material news, volatility controls, regulatory questions and operational events. Exchange halts resume through a quotation period and a reopening auction before continuous trading starts.
Types of trading halts and halt codes
Nasdaq’s T1 code identifies news pending; LUDP identifies a volatility trading pause. An SEC trading suspension and a market-wide circuit breaker follow their own authorities and procedures.
Formula
Reopening gap % = (reopening price − last pre-halt price) / last pre-halt price × 100- Use the last trade before the halt and the reopening auction price.
- Positive values indicate a higher reopening; negative values indicate a lower reopening.
Trading halt example: a news-pending halt and reopening
XYZ last trades at $36.00 before a news-pending halt. It reopens through an auction at $41.40 with 900,000 shares paired.
- Dollar gap: $41.40 − $36.00 = $5.40
- Percentage gap: $5.40 / $36.00 × 100% = 15%
- Reopening notional: 900,000 × $41.40 = $37,260,000
XYZ’s auction pairs 900,000 shares at $41.40, a $37,260,000 execution. The reopening price is $5.40, or 15%, above the $36.00 pre-halt trade.
XYZ last trades at $36 before a news halt. In the example, the issuer releases news ten minutes later, quotations resume at minute 35 and the auction occurs at minute 40.
The auction pairs 900,000 shares at $41.40, a $37,260,000 print that lands 15% above the last trade. A trader short the stock into the halt reopens $5.40 a share underwater.
How trading resumes after a halt
The exchange announces quotation and trading times, collects orders during the quotation period and sets the matched price in the auction; continuous trading starts after that.
News halts, volatility pauses and operational interruptions follow different procedures, so watch the exchange’s halt notice for the quotation and resumption times.
Orders and positions after a reopening
Review each order’s status, quantity and participation in the auction. Compare the opening match with subsequent price and volume to understand the trading response. An options position needs a fresh read after the reopening: put the reopening price and the options’ new implied volatility in the options profit calculator, and the payoff shows what the position is worth now.
Limitations of trading halts
- Plan for the cause, not the clock. A volatility pause is brief, a news halt lasts until the information is out, and a regulatory suspension can run much longer.
- Size the position for the reopening gap. A halt pauses executions, not price risk: information and orders accumulate while trading stops, and the example reopens 15% above the last pre-halt trade.
- Expect a stop to fill at the reopening price. A broker-held stop can activate when eligible prices resume and fill far beyond the stored stop price.
- Ask the broker how each open order is handled. Whether it stays queued, can be canceled or modified, or joins the reopening auction turns on the order type, venue, broker and halt reason.
Bottom line
A trading halt pauses executions for news, volatility, regulatory or operational reasons, and exchange halts resume through a quotation period and a reopening auction. Check the halt code and published resumption times, review how each open order is handled, and size positions for a reopening price that can gap far from the last trade.
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Sources and Further Reading
How entries are sourced, calculated and updated: editorial methodology.