Recently, many people have asked me, do day trades have to be sold on the same day?

Actually, this is a very good question because many beginners are still a bit unclear about the rules of day trading in the Taiwan stock market.

First, let’s state the conclusion: the essence of day trading is buying and selling on the same day, but whether you "must sell on the same day" needs to be clarified.
If you are doing cash stock day trading or margin trading day trading, then indeed, buying today and selling today is required—that’s what defines day trading.
But if you are trading futures, options, or contracts for difference (CFDs), which are inherently T+0 products, there is actually no strict requirement to sell on the same day.

My understanding is this: day trading involves using margin financing and securities lending provided by brokers to achieve T+0 trading under a T+2 settlement system.
Simply put, if you buy TSMC today and sell it within the same day, that counts as a day trade.
In this process, the broker acts as an intermediary—buying and selling the same number of shares, with securities lending stock inventory unchanged, but they collect commissions.
For traders, this means entering and exiting on the same day.

Interestingly, Taiwan’s stock market has allowed day trading for over ten years now.
Since it was opened in 2014, day trading accounts for nearly 40% of trading volume, and the number of participants has been increasing year by year.
Why do so many people like day trading?
Mostly because they want to profit quickly from intraday fluctuations or simply avoid the risks of holding overnight positions.

But here’s an important point: the reason why day trading doesn’t necessarily require selling on the same day isn’t due to regulatory enforcement but because of trading logic.
If you buy on margin but do not close out your short position on the same day, it becomes a margin-held position, which is entirely different—interest costs and risks increase.
Therefore, strictly speaking, the definition of day trading is completing the buy and sell within the same day.
This isn’t an "absolute must," but rather the core definition of day trading itself.

Regarding practical operations, how many times can you day trade the same stock in one day?
In the Taiwan stock market, there is no explicit limit on the number of trades.
As long as you have sufficient funds or credit within trading hours (9:00 am to 1:30 pm), theoretically, you can trade unlimited times.
After hours (from 2:00 pm to 2:30 pm), you can only close out positions that were not settled during regular trading hours.

However, there’s a real-world issue: although there’s no limit on the number of trades, the actual impact is significant.
First, capital constraints—each buy or sell temporarily occupies funds until the hedge is completed.
Second, stock selection restrictions—only stocks designated as eligible for day trading by the exchange can be traded this way, roughly around 200 stocks.
Odd lots (partial shares) are not allowed for day trading at all.

The most painful part is trading costs.
The total cost for a single round-trip trade in cash stocks is about 0.29% (brokerage fee + stamp tax).
Trading five times a day, the total cost jumps to 1.45%.
This means the stock must have a substantial price increase just to break even and make a profit.
I’ve seen many traders who trade frequently, only to find that all their profits are eaten up by transaction costs.

What’s the difference between cash stock day trading and margin trading day trading?
Cash stock day trading uses your own funds—buying and selling on the same day.
Margin trading day trading involves borrowing money or stocks from the broker—borrowing money is called margin trading, borrowing stocks is called securities lending.
Both require similar account opening qualifications—at least three months of account history and at least 10 trades in the past year.
But margin trading also requires a minimum trading amount of NT$250k and the opening of a credit account.

In terms of fees, cash stock day trading has a stamp tax of 0.15% and a brokerage fee of 0.1425%.
Margin trading has a stamp tax of 0.3%, a brokerage fee of 0.1425%, plus an average interest rate of 0.08%.
So, cash stock day trading costs are lower, but it requires sufficient own capital.

Besides stocks, other financial products can also be day traded, many of which are inherently T+0.
Futures are the most common—transaction tax is only 0.02% of the contract value, with total fees around NT$30, high leverage, and high risk.
Options require only a small premium to trade, with a transaction tax of 0.1% and a few dollars in brokerage fees.
CFDs (Contracts for Difference) have the lowest entry barrier—accounts can be opened with just dozens to hundreds of dollars, with spreads as the main cost, making them especially suitable for short-term swing trading.

Does day trading have to be sold on the same day?
From another perspective, the advantage of day trading is closing out the position on the same day, allowing for quick stop-loss and avoiding overnight risk.
In some ways, it can be considered a no-capital business because the settlement system allows for rapid fund transfer.
It avoids the risks of holding overnight positions, and if your judgment is wrong, you can sell immediately.

But the risks are real.
The most common trap is trading on margin without enough cash—this involves leverage, which greatly increases risk.
Some traders use leverage beyond their capacity; if they make wrong moves and don’t cut losses in time, they can suffer huge losses with little profit.
Another issue is the time cost of monitoring the market—day trading requires constant attention to individual stocks, market movements, chip flow, news, etc., much more work than swing trading.

The rules in the US are different.
The US has the Pattern Day Trader (PDT) rule—if your account value is below $25,000, you can only make three day trades within five trading days.
Exceeding that limit results in trading restrictions until your account equity recovers.

Finally, I want to say that day trading doesn’t necessarily have to be sold on the same day; this isn’t a strict regulation but a core trading logic.
If you want to truly participate in day trading, you need to understand the significance of completing buy and sell transactions within the same day.
Whether you choose cash stock day trading, margin trading, or futures and options, controlling costs and managing risks are key to success.
Many are attracted to day trading but haven’t thought carefully about whether they are truly suited for this high-frequency, high-cost, high-risk trading style.