Recently, I’ve seen many people in the community ask whether they can still buy when a stock hits the daily limit up. This is actually a very good question, because many beginners still have some misunderstandings about limit up and limit down.

First, let’s briefly explain what limit up and limit down are. Limit up means the stock price rises to the upper limit within a day. Taking Taiwan’s stock market as an example, the rule is that it cannot exceed 10% of the previous day’s closing price. Conversely, limit down is the lower limit—also 10%. When the stock price stays pinned at that level, the price chart turns into a straight line, so you can spot it at a glance. On the Taiwan stock market, limit up is marked with a red background, while limit down is marked with a green background.

So here’s the key question—can you buy at limit up? The answer is yes. But there’s an important point to get clear: you can place an order to buy when it’s at the limit up, but your order might not be filled immediately, because there are already a large number of people queued to buy at the limit-up price. However, if you want to sell, it can basically be executed right away, because at that moment, the number of people who want to buy far exceeds the number of people who want to sell.

Limit down is basically the opposite. The question “Can I buy at limit down?” also applies here—you can place an order. But if you buy, it will usually be filled immediately, while selling will require waiting in the queue. A practical tip is: if you notice that a stock may hit the limit down, it’s best to place your sell order during the opening auction, because the trading rule is “price priority, time priority”—the earlier you place your order, the higher your priority.

Why does limit up happen? Common reasons include the company releasing strong quarterly results, receiving big orders, or the market hype around a hot theme—such as AI concept stocks or biotech stocks—where stocks may jump directly to the limit up. Locked-up float by major players can also lead to limit up, because there are simply no shares available for sale in the market. Limit down is usually caused by bad news, an earnings blow-up, major players dumping/distributing shares (main force offloading), or market panic. Margin calls can also trigger limit down—in that situation, the sell pressure becomes especially fierce.

Interestingly, the U.S. stock market has no concept of limit up or limit down. Instead, they use a circuit breaker mechanism—when stock prices move too violently, the system automatically pauses trading to cool things down. A market-wide circuit breaker means trading is paused for 15 minutes if the S&P 500 drops more than 7% or 13%; if it drops 20%, trading is halted for the day. For individual stocks, circuit breakers trigger if a single stock’s price rises or falls more than 5% within a short period, which temporarily suspends trading.

In real-world trading, when facing situations like “Can I buy when it hits the limit up?”, the most important thing is to make a rational judgment. Don’t chase the price blindly. First, find out why the stock hit the limit up—whether it’s genuinely driven by strong positive fundamentals or just short-term hype. If a high-quality stock is dragged down by market sentiment and hits the limit down, you may consider building a small position. And when you see a stock hit the limit up, don’t rush to chase it—waiting and observing is often the smarter choice.

Another approach is to trade related stocks. For example, if TSMC hits the limit up, other semiconductor stocks often move along with it, so you can look for opportunities among those related names. Or, if you want to avoid the limit up/limit down restrictions on a single stock, you can consider trading the same company on the U.S. stock market—for instance, TSMC on the U.S. market can be traded, as it has an available listing there. This way, the trading can be more flexible.