Trading Halt
An exchange pause in trading — usually volatility circuit breakers (LULD) or pending news.
What it means
US exchanges halt a stock when price moves outside allowed volatility bands (LULD — limit up/limit down) or when material news is pending. Trading stops for minutes; quotes freeze; then the stock reopens through an auction, often at a very different price.
For automated systems halts are a data problem as much as a risk problem: the feed goes quiet, indicators built on "seconds since last trade" misbehave, and orders resting at the halt can reopen deep underwater.
Why traders care
- Halt-prone movers (small caps up 50%+) are precisely where scanners point — know the mechanics before automating them.
- A reopen auction is a liquidity event: spreads and slippage are at their worst right after it.
Related terms
Educational content, not investment advice. Engine details describe how TraderWe computes this value; other platforms may define it differently.