If you hold Korean shares from abroad, three numbers determine your after-tax return: a 22% default withholding on dividends (frequently reduced to 10-15% under a tax treaty), a securities transaction tax — 0.2% on KOSPI sales as of 2026 — charged on every sale regardless of profit, and — for the overwhelming majority of foreign portfolio investors — a 0% capital-gains rate, thanks to an exemption for on-exchange sellers who own less than a quarter of a company. Domestic Korean tax guides rarely frame any of this for someone filing in another country, which is what this guide does.
The topic is timely for a concrete reason: foreign money has been moving through Seoul in size. On September 23, 2026, foreign investors net sold 494.22 billion won on the KOSPI, capping a stretch that swung from heavy selling in mid-September to a few sessions of modest buying just before. Every foreign holder behind those flows faces the same withholding and transaction-tax math. The mechanics below, however, do not change with the headlines — they apply to every Korean dividend and every sale under the rules currently in force, though rates and exemptions are revised from time to time, as the transaction tax’s own recent history shows.
The Three Taxes at a Glance
| Tax | Default rate for non-residents | When it applies | Who handles it |
|---|---|---|---|
| Dividend withholding | 22% (20% national + 2% local surtax); treaty rates typically 10-15% | Every cash dividend, at payment | Withheld at source by the paying agent / custodian |
| Securities transaction tax | 0.20% of sale proceeds on KOSPI trades as of 2026 (0.05% STT + 0.15% rural-development surtax) | Every sale, profitable or not; never on purchases | Deducted automatically by your broker at settlement |
| Capital-gains tax | 0% for most foreign portfolio investors (exemption); otherwise withheld | Only if you fail the exemption tests below | Withheld by the buyer-side agent if applicable |
Note what is absent: for a typical portfolio investor, there is no Korean tax return to file. Withholding is final, and the transaction tax is invisible inside your broker’s net settlement figure. Your real work is documentation — getting the treaty rate applied before payment rather than reclaiming it afterward.
Dividend Withholding: 22% by Default, Less by Treaty
Korea’s statutory withholding on dividends paid to non-residents is 20%, plus a local income surtax of 10% of that amount, for a combined 22%. This is deducted before the cash ever reaches your account. On a hypothetical 1,000,000 won gross dividend, you receive 780,000 won unless a treaty rate has been applied.
Korea maintains tax treaties with most major economies, and dividend articles in those treaties commonly cap the rate at 10-15% for portfolio holders. Under a 15% treaty rate, that same 1,000,000 won dividend delivers 850,000 won — a 70,000 won difference on every million, purely from paperwork.
How the treaty rate is applied at source
- You (or your global custodian) submit an application for the reduced treaty rate, with proof of tax residence, to the Korean withholding agent before the dividend payment date. In omnibus custody structures this flows through your custodian’s standing documentation.
- Since Korea retired its decades-old investment registration certificate system in late 2023, foreign investors identify themselves through passport- or LEI-based registration instead — but the treaty-relief paperwork is a separate step. New registration alone does not trigger the reduced rate.
- Funds and other look-through vehicles face extra scrutiny: Korea generally requires beneficial-owner-level documentation, and an undocumented beneficial owner defaults back to 22% for their slice.
The reclaim path if you were over-withheld
If 22% was withheld when your treaty entitled you to 15%, the excess is recoverable — but only from Korea, via a refund claim filed through the withholding agent or district tax office, within a statutory window that has historically run about five years. This matters because of a trap covered in the mistakes section below: your home country’s foreign tax credit is normally capped at the treaty rate, so the extra seven points are simply lost if you never file the Korean reclaim.
The Securities Transaction Tax: Paid on Every Sale, Win or Lose
Korea levies a securities transaction tax — jeunggwon georaese in Korean — on the gross proceeds of every sale of listed shares. The combined rate for KOSPI trades (the tax itself plus a rural-development surtax component) was restored to 0.20% effective January 1, 2026 — 0.05% securities transaction tax plus 0.15% Special Tax for Rural Development — following the repeal of the Financial Investment Income Tax, after several years in which the government had trimmed it into the 0.15-0.2% range; check the current schedule on the KRX portal before modeling costs precisely. Three features define it:
- Sale-side only. Buying is free of the tax. A round trip incurs it exactly once.
- Indifferent to profit. It is a turnover tax, not an income tax. Sell at a 30% loss and you still pay it on the full proceeds.
- Fully automated. Your broker deducts it at settlement; you will only see it as a line inside the net proceeds. There is nothing to file and, importantly for cross-border investors, generally nothing to credit at home — it is not an income tax under most foreign-tax-credit rules, so treat it as a trading cost, like commission.
The practical consequence: for a small foreign holder who enjoys the capital-gains exemption, the transaction tax is usually the only tax on the capital side of the trade, and it scales with turnover, not with success. High-turnover strategies pay it constantly; buy-and-hold strategies barely notice it.
Capital Gains: Why Most Foreign Portfolio Investors Pay Zero
Korea’s domestic rules do tax non-residents on Korean-source share gains — but a broad exemption swallows the typical case. A non-resident’s gain on listed shares is exempt when, roughly stated, both of the following hold:
- The sale is executed on-exchange (through the KOSPI or KOSDAQ market, not as an off-exchange block or private transfer), and
- You, together with related parties, held less than 25% of the company at all times during the year of sale and a multi-year lookback period (historically five years).
Fail either test and withholding applies at roughly the lesser of 11% of gross sale proceeds or 22% of the net gain — although many treaties then override this and assign taxing rights on share gains exclusively to your home country, restoring the practical exemption. The order of analysis is: exemption first, treaty second, withholding only if both fail.
Two groups should read the fine print rather than relying on the headline exemption: strategic or activist holders whose stakes approach the 25% threshold (related-party aggregation is easy to trip), and anyone selling off-exchange, including participants in tender offers or negotiated blocks, where the on-exchange condition fails even for tiny stakes.
Worked Example: Reading a Real Foreign-Flow Number — and What It Costs in Tax
Foreign activity in Seoul is published daily, and the units confuse newcomers. Here is an actual figure and how to read it, step by step.
The figure: foreign investors’ net flow on the KOSPI was -4,942.2 as of September 23, 2026, in units of 100 million won (the Korean unit eok).
- Convert the unit. One eok is 100 million won, so -4,942.2 eok = -494.22 billion won. The minus sign means foreigners sold more than they bought that session.
- Convert to dollars for scale. At the USD/KRW rate of 1,362.50 (September 24, 2026 close), 494.22 billion won is roughly USD 363 million of net selling.
- Apply the tax lens. Every won of that selling incurred the transaction tax. Even taking only the net figure as a floor — gross sell volume is always larger — 494.22 billion won of sales at the 0.20% rate in force generates about 988 million won (roughly USD 0.73 million) of transaction tax in a single session, paid by foreign sellers whether or not those trades were profitable. That is the turnover tax working exactly as designed.
- Read it in context, not isolation. The days around it (all in eok won, as of September 2026) ran from heavy selling on September 10-17 (between roughly -15,458 and -33,363 per day) to modest buying on September 18-22 (+4,486, +117, +494) before the -4,942.2 print. Single-day flow numbers are noisy; the multi-day path is the signal.
Where to find these numbers yourself: daily investor-type flows are on the KRX data portal and Naver Finance; aggregate investor deposits — tuja-ja yetakgeum, the cash sitting in brokerage accounts, which stood at about 100.98 trillion won as of September 22, 2026 — are published in KOFIA statistics.
Common Mistakes That Cost Real Money
- Missing the record-date settlement window. Korea settles trades on a T+2 cycle. To be on the shareholder register at a record date, you must buy at least two trading days before it; the ex-dividend date falls one trading day ahead of the record date, and buying on the ex-date gets you nothing.
- Filing treaty paperwork after the dividend. Relief at source is cheap and immediate; reclaiming over-withheld tax from Korea takes documentation, patience, and months. Confirm your custodian’s standing treaty documentation before any record date you care about.
- Assuming the home-country credit fixes over-withholding. It does not. If your treaty rate is 15% and Korea withheld 22%, most foreign-tax-credit regimes cap the credit at 15%. The remaining seven points are recoverable only via a Korean refund claim.
- Modeling the transaction tax as creditable. It is a turnover levy, not an income tax; budget it as a trading cost alongside commissions and FX conversion.
- Ignoring related-party aggregation near 25%. The capital-gains exemption tests combined holdings over a multi-year lookback, not just your entity’s stake on the sale date.
FAQ
Do I need to file a Korean tax return as a foreign portfolio investor?
Generally no. Dividend withholding is a final tax for non-residents, the transaction tax is deducted by your broker automatically, and exempt capital gains create no filing obligation. Filing only enters the picture for refund claims or for investors who fail the capital-gains exemption without treaty protection.
Can I recover dividend tax that was withheld at 22% instead of my treaty rate?
Yes. A refund claim can be filed through the Korean withholding agent or the competent tax office, with proof of your tax residence for the relevant year, within a statutory window that has historically been about five years. Custodians routinely handle this, but usually only if you ask.
Does the capital-gains exemption cover KOSDAQ stocks too?
Yes. The on-exchange condition is satisfied by regular trades on either the KOSPI or KOSDAQ market. Off-exchange transfers — negotiated blocks, tender offers, private sales — fall outside it regardless of how small your stake is, so the treaty analysis becomes essential in those situations.
Is the securities transaction tax ever charged on purchases?
No. It applies only to sales. This asymmetry means position-building is tax-free on the capital side, while every exit — rebalancing included — carries the levy on full proceeds.
Sources
- KRX data portal — daily investor-type trading flows and market data (data.krx.co.kr)
- Naver Finance — daily foreign net buy/sell by market (finance.naver.com)
- KOFIA statistics — investor deposits and margin-loan balances (freesis.kofia.or.kr)
- Bank of Korea ECOS — exchange rates and macro statistics (ecos.bok.or.kr)
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.