Gap Up and Gap Down: When a Stock Opens Far From Its Last Close

By Imperialpedia Staff

A gap up or gap down describes a stock opening significantly above or below where it closed the previous session, leaving a visible gap on a price chart where no trading actually occurred at the prices in between. Gaps typically happen because something material — earnings, news, an analyst upgrade or downgrade — emerged while the regular market was closed.

Why Gaps Happen at All

During regular trading hours, a stock's price generally moves in continuous, incremental steps as buyers and sellers trade at closely spaced prices. Overnight, no such continuous trading occurs on the primary exchange, so when new information arrives, the next open reflects wherever supply and demand settle at once, rather than gradually working through the intermediate prices.

Gap Fills

Traders often talk about whether a gap "fills," meaning the price eventually retraces back to the pre-gap level. Some gaps fill within the same day as buyers and sellers reassess the news, while others, especially those driven by a genuine, lasting change in a company's outlook, never fill at all.

Gaps Concentrate Risk for Overnight Positions

Anyone holding a position overnight is exposed to gap risk, since stop-loss orders sitting at a specific price offer no protection against a gap that jumps straight past them. This is one of the clearest examples of how overnight and weekend holding periods carry a distinct kind of risk that intraday trading doesn't.

Table of Contents

Gap Up and Gap Down: When a Stock Opens Far From Its Last Close

Why Gaps Happen at All

Gap Fills

Gaps Concentrate Risk for Overnight Positions

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