Circuit Breaker — Trading Wiki

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Published by TradeHQ. Site creator: Anuga Weerasinghe. This page has no recorded editorial review date; the About page explains the site's editorial approach.

What Circuit Breaker means

A rule-defined trading pause. US market-wide thresholds use S&P 500 declines of 7%, 13% and 20%, with time-of-day conditions; individual-security and other-market rules differ.

In depth

Circuit breakers are rule-defined trading pauses. In the US market-wide example described by NYSE, declines from the previous S&P 500 close trigger three levels: 7%, 13% and 20%. In a regular session, a Level 1 or Level 2 event before 3:25 p.m. Eastern leads to a fifteen-minute halt; those levels at or after that time do not halt trading. Level 3 ends trading for the day. Check the current exchange rules and special-session arrangements rather than applying this example to every venue. Individual-security Limit Up-Limit Down rules are separate from a market-wide halt: price bands and pauses depend on the applicable plan.

Neither mechanism guarantees an exit price or prevents losses, and a reopening can occur at a different price. Other markets and asset types can have different controls. For a hypothetical comparison, distinguish a 7% S&P 500 decline early in a regular session from the same decline after 3:25 p.m., then compare a Level 3 event. These are rule-reading exercises; TradeHQ does not execute exchange orders or reproduce every halt and reopening condition.

Key points

• US market-wide halts at S&P 500 declines of 7%, 13%, and 20%
• Individual stock halts (LULD) prevent trades outside price bands
• Venue-specific crypto trading controls vary; do not assume US equity halt rules apply

Why it matters when you are learning

Read the current venue rules and distinguish a market-wide halt from an individual-security pause. A halt does not prevent every loss or establish a post-reopening opportunity.

Worked exercise and its limits

With a hypothetical prior S&P 500 close of 5,000, declines of 7%, 13% and 20% correspond to 4,650, 4,350 and 4,000. Apply the official time-of-day rules before predicting a halt; individual-security pauses use different rules.