{
  "id": "c87cba1f-959c-5dd1-ab68-3479fce2b5b8",
  "slug": "trading-halt",
  "term": "Trading Halt",
  "aliases": [],
  "category": "Market Microstructure",
  "category_slug": "market-microstructure",
  "difficulty": "basic",
  "definition": "A trading halt is a temporary suspension of trading in a specific security or across an entire market, imposed by an exchange, regulator, or clearinghouse to allow the orderly dissemination of material information, prevent disorderly price movements, or address technical failures. Halts protect market integrity by ensuring participants can respond to new information on equal footing.",
  "key_takeaways": [
    "Trading halts can be issuer-requested (pending news), regulatory (SEC or exchange-initiated), or market-wide (circuit breaker triggered by index-level declines).",
    "Market-wide circuit breakers in the U.S. halt all equity trading for 15 minutes if the S&P 500 falls 7% or 13% from the prior close; a 20% decline triggers an all-day halt.",
    "Individual stock halts triggered by the LULD (Limit Up-Limit Down) mechanism pause trading when prices move more than a specified band from recent averages.",
    "During a halt, no new orders can be submitted or existing orders filled; however, orders resting in the book may remain queued for execution upon reopening.",
    "Extended halts create significant liquidity and settlement risk for funds using TWAP/VWAP algorithms or holding concentrated positions in halted securities."
  ],
  "detailed_explanation": "Trading halts are one of the most visible interventions in market microstructure, representing a deliberate interruption of the normal price discovery process. While halts introduce friction and can create adverse price gapping upon reopening, they serve the crucial function of leveling the informational playing field—ensuring that all market participants have access to material disclosures before trading resumes and that extreme volatility does not feed on itself in a self-reinforcing spiral.\n\nHalts fall into several distinct categories. News-pending halts are requested by the issuer (e.g., a company) or its listing exchange when a significant announcement—a merger agreement, material accounting restatement, or regulatory action—is imminent. The halt gives the company time to release the news via wire services and allows market makers and investors to digest the information before trading resumes. These halts typically last 30 minutes to several hours and frequently result in material price gapping upon reopening, particularly for merger announcements where risk arbitrage opportunities emerge instantly.\n\nRegulatory halts are imposed unilaterally by the SEC or an exchange when there is an extraordinary event affecting market integrity: for example, concerns about security of trading systems, unusual order imbalances, or evidence of fraud. Under SEC Rule 12(k), the Commission has authority to suspend trading in any OTC security for up to 10 trading days and to halt exchange-listed securities temporarily. FINRA can also halt trading in OTC markets for any security where abnormal trading activity is detected.\n\nMarket-wide circuit breakers were formalized after the 1987 stock market crash and revised substantially after the May 6, 2010 Flash Crash. Under current SEC rules, market-wide circuit breakers are triggered by S&P 500 declines of 7% (Level 1), 13% (Level 2), and 20% (Level 3) from the prior day's closing price. Level 1 and 2 halts last 15 minutes each and apply only if triggered before 3:25 PM ET; Level 3 halts immediately suspend trading for the remainder of the day. These rules coordinate across all U.S. equity exchanges under the Market-Wide Circuit Breaker (MWCB) mechanism.\n\nFor individual securities, the Limit Up-Limit Down (LULD) mechanism, implemented in 2013, prevents trades from occurring outside a defined price band—typically 5% for S&P 500 and Russell 1000 stocks (10% for other stocks) from a reference price calculated as the rolling average of trades over the preceding 5 minutes. If the best bid or offer hits the LULD band, trading pauses for 15 seconds to allow orders to refresh; if the imbalance persists, a full 5-minute trading pause is triggered. LULD has largely replaced the older single-stock circuit breaker rules and has been credited with significantly reducing mini-flash crash events in individual stocks.",
  "example": "On March 16, 2020, during the COVID-19 market sell-off, the S&P 500 opened sharply lower and fell 7% from the prior close within the first four minutes of trading, triggering a Level 1 market-wide circuit breaker at 9:34 AM ET. All U.S. equity exchanges halted trading simultaneously for 15 minutes under the MWCB protocol. When trading resumed at 9:49 AM, the market continued to decline, falling a total of 12% by end of day—the third-worst single-day decline in S&P 500 history. A hedge fund running a TWAP algorithm to sell $200 million in S&P 500 futures had its algorithm automatically pause during the halt; upon resumption, the algorithm recalibrated its execution schedule to account for the lost 15 minutes of trading window, concentrating subsequent selling into a shorter remaining session and modestly increasing market impact.",
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  "formula_latex": null,
  "interactive_type": null,
  "calculator_id": null,
  "related_terms": [
    "arbitrage",
    "best-execution",
    "circuit-breaker",
    "clearing",
    "equity",
    "exchange",
    "finra",
    "hedge-fund",
    "layering",
    "market-impact",
    "price-discovery",
    "risk-arbitrage",
    "settlement",
    "stock",
    "twap-algorithm"
  ],
  "backlinks": [
    "locked-limit"
  ],
  "cross_references": [
    "arbitrage",
    "circuit-breaker",
    "equity",
    "exchange",
    "finra",
    "hedge-fund",
    "market-impact",
    "price-discovery",
    "risk-arbitrage",
    "stock",
    "twap-algorithm",
    "volatility"
  ],
  "tags": [
    "level:basic",
    "cat:market-microstructure"
  ],
  "asset_classes": [],
  "regulators": [],
  "see_also": [],
  "sources": [],
  "wordcount": 790,
  "checksum": "9533df3458e37ef1",
  "version": "2026.05.03",
  "license": "CC-BY-4.0",
  "updated_at": "2026-09-07T02:15:24+00:00",
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