What Is an ISA Account? Open One as Soon as Possible!

The ISA account was introduced in 2016. It lets you invest in a variety of financial products (deposits, stocks, funds, etc.), and taxes are calculated by combining all the gains and losses arising from them. The most important point is that you pay no tax at all up to a certain amount.
Types of tax benefits
General type: tax-exempt up to 2,000,000 won; returns above 2,000,000 won are taxed at only 9.9%
Low-income/youth type: tax-exempt up to 4,000,000 won; returns above 4,000,000 won are taxed at only 9.9%

[Example]
Example 1: General-type ISA (total return of 1,500,000 won)
Kim Cheol-su opened a general-type ISA and invested in various products for 3 years.
At maturity, his total return was 1,500,000 won.
Since the tax-free limit for the general type is 2,000,000 won, the entire 1,500,000 won is tax-exempt.
Kim Cheol-su receives the full 1,500,000 won.
In a regular account instead of an ISA => 231,000 won in tax

Example 2: Youth-type ISA (total return of 5,000,000 won)
Lee Young-hee (age 28) opened a youth-type ISA and invested for 5 years.
At maturity, her total return was 5,000,000 won.
The tax-free limit for the youth type is 4,000,000 won, so:
4,000,000 won: tax-exempt
1,000,000 won (excess): 9.9% tax rate applied → 99,000 won in tax
Lee Young-hee ultimately receives 5,000,000 won - 99,000 won = 4,901,000 won.
In a regular account instead of an ISA => 770,000 won in tax

Example 3: Offsetting losses and gains
Park Ji-min's ISA account: a 1,000,000 won loss on stock investments,
a 3,000,000 won gain on fund investments, and a 500,000 won gain on deposits
Total net gain: -1,000,000 + 3,000,000 + 500,000 = 2,500,000 won
For a general-type subscriber, up to 2,000,000 won is tax-free, and the remaining 500,000 won is taxed at 9.9% = 49,500 won paid
Final amount received: 2,500,000 won - 49,500 won = 2,450,500 won
In a regular account instead of an ISA => 539,000 won in tax

In this way, with regular investing, taxes would have had to be calculated separately for each financial product.
In an ISA, losses and gains are calculated together and you are exempt from tax up to a certain amount, so the tax-saving effect is significant.