When investing in stocks, people often focus only on return rates and end up overlooking what’s truly important. One big one is transaction fees—something that has a surprisingly huge impact on your final profit. I recently compared securities brokerage fees properly, and the difference really was significant.

First, let’s sort out what fees you run into when trading stocks. Each time you buy and sell shares, you pay your brokerage a commission fee. You also pay fees to institutions such as the exchange and the Korea Securities Depository, and when trading overseas stocks, you’ll even incur currency exchange fees. For domestic stocks, the fee is usually about 0.1% to 0.15%, while overseas stocks are much more expensive at around 0.25%.

When you compare the fees of the “top 5” securities firms, the differences are truly noticeable. Mirae Asset Securities charges 0.136% for domestic trades and 0.25% for overseas trades, and it runs a 90-day free event for new customers. Korea Investment & Securities is also similar at 0.147% for domestic and 0.25% for overseas, with a 3-month free benefit. Samsung Securities charges 0.147216% plus a fixed fee of 1,500 won for small trades. Kiwoom Securities is extremely cheap at 0.015% when you trade through its platform, Hero Mungmun 4. Shinhan Investment Corporation charges 0.1391639% plus 2,000 won for trades of 30 million won or less. Looking at this, you can clearly see that brokerage fees can change dramatically depending on the trade amount and the platform.

If you calculate why fees are so important, you’ll feel it for sure. Suppose you invest 1 million won and make 10 trades, earning a 10% profit each time. When the fee is 0.1%, your final profit comes to 2.57 million won; when the fee is 0.2%, it drops to 2.54 million won—about a 20,000 to 30,000 won difference. The more trades you make and the larger the amounts, the more this gap grows exponentially. Especially if you frequently do small day trades, fixed fees can become a real problem. For example, with Samsung Securities: making 100 trades of 1,500 won each results in fixed fees of 150,000 won by itself.

So how can you reduce fees? First, you need to compare each brokerage’s fees accurately. It’s important to figure out which brokerage is the cheapest for your typical trading amount range and for the platform you use most. If you’re a new customer, be sure to take advantage of the fee-free events each brokerage offers. Most waive fees for 3 months to 1 year, and in many cases you can choose when to apply, so it’s best to apply right before you start actively trading.

Your trading method also matters. Don’t buy and sell too many times in smaller chunks—executing a single trade is helpful for saving on fees. If you do a lot of small-amount trades, be careful, because fixed fees can cause even bigger losses. When trading overseas stocks, you also need to watch currency exchange fees. Securities firms often offer worse exchange rates than banks or dedicated exchange platforms. One way to minimize losses is to exchange currency when rates are favorable in advance, or check the brokerage’s preferential exchange-rate benefits.

In the end, choosing a brokerage that matches your trading style is the key. If you frequently do small day trades, choose a place with no fixed fees. If you trade large amounts at once, choose a brokerage where the fee decreases as the transaction amount increases. Comparing brokerage fees may seem complicated, but if you do it properly once, you can save a truly large amount of money over the long term.