Why earnings matter for the chart
US listed companies report results such as revenue and profit every quarter. Earnings are the most direct new information about what a company is worth, so even a usually quiet large cap often makes its longest candle of the year around a report. The market tends to react less to the reported numbers themselves than to how far they differ from expectations already formed, and to what the company says about the next quarter. That is why a stock can fall on numbers that look good, or the other way round. It is also why checking the next earnings date before reading a chart is a useful habit.
Pre-market and after-hours reports
Most US companies do not report during the regular session; they release results before the open or after the close. The practice avoids sudden disruption during trading and gives investors time to read the release. Where the reaction shows up on the chart depends on the timing.
- Before the open: the first reaction is in pre-market trading, and a gap forms at that day's regular open
- After the close: the first reaction is in after-hours trading, and a gap forms at the next day's regular open
- In Korean time, after-close reports usually land in the early morning and pre-open reports in the evening
- The company's call after the release can move the extended-hours price sharply a second time
Volatility before and after
Before a report, many stocks trade less and move in a narrow range while waiting, and in the options market the prices that reflect expected moves are often higher than usual. Once the report is out and uncertainty clears, those option prices dropping quickly is a widely known effect. On the stock chart, the next regular session often brings a gap, a long candle and volume several times the usual level. Because individual US stocks have no daily price limit, most of this reaction fits into a single daily candle.
Reading the chart after a gap
After an earnings gap, many traders watch whether it holds or gets filled. If the day closes in the direction of the gap on heavy volume, many read it as the market accepting the new information; if the gap is mostly reversed during the session, some see the first reaction as overdone. These are tendencies, not rules. And because extended-hours prices can differ a lot from the regular open, it is better not to decide the next day's direction from the after-hours chart alone. Gaps and gap fills get their own guide.
How indicators get shaken
A single earnings gap can change technical indicators a great deal. Keep in mind that indicator readings right after a report are hard to read the usual way.
- Moving averages: the price jumps by the size of the gap, so short averages turn sharply
- RSI: one big day can push it straight into overbought or oversold territory
- Bollinger Bands and ATR: volatility measures expand and the bands stay wide for a while
- Composite signals: many indicators flip at once, so a rating can reverse in a day
Compared with Korean stocks
Korean companies also disclose results every quarter, and some, like Samsung Electronics, publish preliminary results first after the quarter ends. Disclosures can come out during the session, so the moment the chart reacts can differ from the US. Korean stocks also have a ±30% daily price limit, so a very large reaction can hit the limit and spill into the next day, appearing over several days. On some days a US tech company's earnings seem to shape the next day's move in Korean chip stocks, but remember the one-day date shift between the two markets when reading it.
Check it with this site's live tools
You can see post-earnings changes directly with this site's stock tools. The buy and sell signals tool shows each indicator's rule and current value, so you can compare which indicators changed before and after a report. The large-cap scanner makes large caps with big volume and daily moves stand out right away, and rebasing a reporting stock and an index to 100 on the same day in the stock comparison tool shows how much the report changed its path relative to the index. Prices may be delayed.
Things to keep in mind
This guide explains the marks earnings leave on a chart and is not investment advice. Extended-hours trading right after a report can be volatile and hard to fill, and gaps can make stop orders fill at prices far worse than planned. Confirm earnings dates and times through the company's official announcements.
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