Recently, many beginners have been asking about limit-up and limit-down situations in the Taiwan stock market, so I’ll summarize my experience from the past few years to help everyone avoid pitfalls.

To put it simply, limit-up and limit-down in the Taiwan stock market represent the extreme states of stock price fluctuations. According to the rules, an individual stock’s daily price limit up or down cannot exceed 10% of the previous day’s closing price. Once the stock reaches these upper or lower limits, the price gets locked and can’t move. For example, if TSMC closed at 600 NT dollars yesterday, today it can only rise to a maximum of 660, while the lowest price will be stuck at 540. Many people, seeing this for the first time, think the system is malfunctioning—when in fact it’s simply an extreme imbalance between buy orders and sell orders in the market.

How can you tell whether a stock has hit the Taiwan stock market’s limit-up? The most direct way is to look at the price chart. If it turns into a straight line and doesn’t move, that’s basically it. On the trading screen, limit-up is marked with a red background, and limit-down is marked with a green background—making it easy to tell at a glance. You can also infer things by looking at the order book. At limit-up, buy orders pile up like a mountain while sell orders are almost empty. At limit-down, it’s the opposite: sell orders are full and buy orders are sparse.

A lot of people have a misconception here: they think that once a stock hits limit-up or limit-down, it can’t be traded. Actually, that’s not true. You can still place orders—the difference is mainly in how trades get executed. When a stock hits limit-up, if you place a buy order, it may not fill immediately because there are already many people lined up waiting at the limit-up price. But if you place a sell order, it will basically execute instantly, because the number of buyers is overwhelming. Conversely, when a stock is at limit-down, buy orders may get filled quickly, but sell orders must line up and sometimes have to wait for a long time.

When it comes to what to do if a stock is locked at limit-down, this is a major pain point for many people. Once a stock hits limit-down, the chance that it will continue to fall over the next few trading days is usually very high—so absolutely don’t wait until it truly hits limit-down to sell. By then, it will only fall further the more you sell. The smartest approach is: as soon as you notice the stock might hit limit-down, place a sell order during the call auction/opening auction. The trading rule is “price priority, time priority.” The earlier you place your order, the higher your position in the queue, and the better your chance of getting filled. After your order is successful, it’s best not to cancel it randomly. Many people see that their order hasn’t been sold and then panic-cancel and re-place it, but this actually pushes their order to the back of the queue, making it even harder to get filled. Also, note that for limit-down stocks, in the final 10 to 15 minutes before market close, there may sometimes be a brief release of liquidity—this can be the last chance to get out that day.

What kinds of situations lead to a limit-up in the Taiwan stock market? Usually, it’s driven by positive news, such as an outstanding earnings report, a sharp surge in EPS, or winning a large order. The market also loves chasing hot themes—stocks tied to AI concepts or biotech, for example—these often jump straight to limit-up after a single surge. When large players lock up the float, limit-up becomes more likely too: continuous net buying by foreign investors and investment trusts, or major players tightly locking up the shares of mid- and small-cap stocks, which means retail investors may not be able to buy at all.

The reasons for limit-down are the opposite. Negative news shocks are a key factor: things like earnings disasters, company scandals, or an industry downturn can trigger panic selling pressure. Systemic risk can also cause collective limit-downs—such as during the COVID-19 outbreak, when many stocks basically just “lay down” and hit the floor. Other common causes include major holders dumping shares and margin call liquidations, while a technical breakdown clearly signals the same direction.

When you encounter a limit-up or limit-down in the Taiwan market, the most important thing is to stay rational. The most common mistake beginners make is blindly chasing upswings or selling in panic. But first, you need to figure out why the stock hit limit-up or limit-down. If it hit limit-down but the company itself has no fundamental problems—just being dragged down by market sentiment—then it may very well rebound. In that case, holding or making a small initial position can be the better move. And if you see a stock at limit-up, don’t rush to chase it. Confirm first whether there are truly strong reasons supporting the continuation of the rally. If you’re not sure, it’s better to wait and observe.

Another approach is to trade related stocks. When a stock hits limit-up due to positive news, you can consider buying upstream and downstream suppliers or similar companies, which often move along with it. Some Taiwanese stocks are also listed on U.S. exchanges. For example, you can buy TSMC in the U.S. market—placing trades via a foreign broker or an overseas securities account is also a good option.

One more thing: the U.S. stock market has no limit-up/limit-down mechanism. Instead, it uses circuit breakers. When the S&P 500 falls by more than 7% or 13%, the entire market takes a 15-minute break, and if it drops to 20% that day, trading stops for the day. If individual stocks move up or down by more than 5% within a short period, trading may also be paused for a time. The design is different, but the purpose is the same: to prevent excessive market volatility.