Korea's Dual Tax System for Stock Sellers
Somewhere around KRW 148.3 trillion in foreign capital left Korean equities in the first half of 2026. And yet KOSPI nearly doubled between May 2025 and January 2026, powered almost entirely by domestic retail buying. Foreigners were heading for the exits while Korean households kept piling in. Here's the piece that explains it: a retail investor can sell Samsung or SK Hynix shares and pay tax only on the sale price, never the profit, as long as their stake stays under KRW 1 billion. The tax code picked its winners a long time ago. It just took a market crash in foreign flows to make that visible.
- 0.20% securities transaction tax: applied to all sales on KOSPI and KOSDAQ, win or lose.
- KRW 1 billion holding threshold: the line separating ordinary retail investors from "large shareholders" for tax purposes.
- 1-2% ownership stake: also triggers large-shareholder status even below the KRW 1 billion mark, so size alone isn't the only trigger.
- 20-25% capital gains tax: the rate applied only to large shareholders and sellers of unlisted stock.
- 11% flat tax: a separate rate applied to derivatives gains, including KOSPI 200 futures and options.
What this means in practice: the tax bill on a KOSPI trade depends far more on how much stock someone holds in a single company than on how much money they actually made. Retail investors trading under the KRW 1 billion threshold trade tax-free on gains, full stop, and that's a huge part of why KOSPI turnover has stayed so stubbornly high. Small and mid-sized retail investors are the clear winners here, and that built-in edge is a big reason Korean households keep churning through KOSPI names the way they do. That edge looks even sharper once you compare it to what these same investors face the moment they look past Korea's borders.
What This Means for KOSPI Investors Today
A typical retail investor buying and selling Samsung Electronics or SK Hynix shares pays only the 0.20% transaction tax on the sale price, nothing on the profit. Cross the KRW 1 billion threshold in a single stock, though, and the math changes completely: gains above that line get taxed at 20-25%, stacked on top of the same 0.20% transaction levy.
- Overseas stock gains: taxed at 22% (20% base plus 2% local surtax) with only a KRW 2.5 million annual deduction, a far heavier burden than domestic KOSPI trades under the KRW 1 billion mark.
- January 2026 tax reform: restructured dividend taxation for firms and investors to encourage higher payouts, part of a broader push tied to Korea's corporate governance overhaul.
- KRW 148.3 trillion (USD 96.7 billion): the widely cited figure for net foreign selling of Korean equities in the first half of 2026, driven by semiconductor profit-taking, global rebalancing, and won depreciation.
- Financial Investment Income Tax (금투세): a proposed reform that would have taxed capital gains more broadly across retail investors. Lawmakers have delayed it repeatedly amid political resistance.
Here's the asymmetry, plainly: domestic retail money keeps flowing into KOSPI partly because the tax code rewards staying under the large-shareholder line, while diversifying overseas means eating a heavier, far less forgiving tax bill. That gap goes a long way toward explaining why Korean households funded the entire 2025-2026 rally while foreign institutions were busy pulling a record amount of capital out the other door. So the tension from the opening resolves into something pretty concrete: KOSPI's structure isn't some puzzle about investor psychology. Lawmakers built a tax code that rewards staying under the KRW 1 billion line, and Korean retail investors responded exactly the way you'd expect. Anyone making cross-border portfolio decisions needs to price in that incentive before assuming the rally says anything about fundamentals.