gap fill explained simply

A gap fill refers to the market phenomenon where a security's price trades back to a previous price level that was skipped over, creating a 'gap' on a chart.

A gap is a discontinuity on a security's price chart that occurs when the opening price is significantly different from the previous closing price, leaving an empty space. This often happens due to news events, earnings reports, or other factors that influence market sentiment outside of regular trading hours. When a stock price moves from $50 at closing to $55 at opening the next day, there is a $5 gap. A gap fill occurs when the price eventually trades back into this empty price range, effectively 'filling' the area that was previously skipped.

For example, if a stock closed at $100 on Monday and then opened at $105 on Tuesday due to positive news, an upward gap of $5 would be present on the chart. If, over the next few days or weeks, the stock's price declines back to the $100 mark, it would be considered to have 'filled' this specific gap. Gaps can occur both upwards (when the price opens higher than the previous close) and downwards (when the price opens lower than the previous close). The concept of a gap fill suggests that there is a tendency for the market to eventually revisit these prices, although this is not guaranteed for every gap. The movement back to the previous price level indicates a resolution of the initial abrupt price change.

Another illustration could be a stock closing at $75, only to open at $70 the next morning due to unexpected negative news. This creates a $5 downward gap. Should the stock then rebound and trade back up to the $75 level within a subsequent trading period, that particular downward gap would have been 'filled.' Traders often observe these patterns as potential indicators of future price movements or areas of support and resistance.

Why it matters

Understanding gap fills can help options traders anticipate potential price reversals or continuations, influencing strategy selection for puts or calls.
Identifying a gap fill might guide the selection of appropriate strike prices for options contracts, aiming for areas that a stock's price may revisit.
Recognizing confirmed gap fills can inform decisions about optimal entry and exit points for options trades, aiding in more effective risk management.
The presence of an unfilled gap may suggest areas of potential support or resistance, which could influence expectations for future options volatility.

Common mistakes

Assuming all gaps will be filled quickly can lead to premature options trades that expire worthless if the underlying asset's price trend continues.
Ignoring the specific context of a gap, such as a major news event or earnings release, and trading solely on the gap pattern can easily lead to misjudging market direction.
Misinterpreting the potential duration for a gap fill, which can take days, weeks, or even never occur, leading to purchasing options contracts with incorrect timeframes.
Over-leveraging financial positions based purely on the expectation of an immediate gap fill can result in significant capital losses if the market moves against the anticipated direction.

FAQs

What causes a gap in a stock's price?

Gaps are often caused by significant news events, such as earnings reports, mergers, or economic data, released when the market is closed, leading to a substantial opening price change.

Does every gap get filled?

No, not every gap is filled. While many gaps do eventually get filled, some may remain unfilled for extended periods, or indefinitely, depending on market conditions and sentiment.

What is the difference between an 'up' gap and a 'down' gap?

An 'up' gap occurs when the opening price is higher than the previous close. A 'down' gap occurs when the opening price is lower than the previous close, both creating discontinuities on charts.