Korean Retail Investor Tax Guide — Overseas Stock Capital Gains Tax Complete Guide
Basic Deduction · Tax Rate · Filing Method · Tax-Saving Strategies

① Introduction — Ignoring Tax Can Cut Your Returns in Half

Imagine you earned a 30% return on US stocks — 10 million KRW turned into 13 million KRW. Sounds great. But what many Korean retail investors ("서학개미") don't realize is that 77,000 KRW in taxes may be due on that 3 million KRW gain. And if you don't file? The penalty — 20% of the original tax — comes on top.

Korean overseas stock tax sounds complicated, but the core is simple: 2.5 million KRW annual deduction, 22% rate, file in May. This guide covers everything from calculating your tax to filing on HomeTax to legally minimizing what you owe.

② The Overseas Stock Tax Framework at a Glance

There are two types of taxes on overseas stock investments: capital gains tax on profits from selling shares, and dividend income tax on dividends received. Securities transaction tax (0.18% on domestic stock sales) does not apply to overseas stocks.

③ Capital Gains Tax — Step-by-Step Calculation

The calculation involves five steps. Here's how it works with a concrete example.

Step 1. Calculate the Gross Gain

Gross Gain = Sale Price − Cost Basis − Necessary Expenses (commissions, fees)

Step 2. Convert to KRW (Critical Step)

All amounts must be converted to Korean Won (KRW). The conversion rule:

• Cost Basis (KRW) = USD purchase price × exchange rate on purchase date
• Sale Proceeds (KRW) = USD sale price × exchange rate on sale date

The exchange rate used is the "standard trading rate" (기준환율) published by the Korea Customs Service. Your brokerage records this automatically in your trade history.

Step 3. Net Gain/Loss Offset (손익통산)

If you traded multiple stocks in the same year, combine all gains and losses across all overseas positions.

Net Gain = Total Gains − Total Losses

Step 4. Subtract the 2.5 Million KRW Annual Deduction

Every year, the first 2.5 million KRW of net overseas stock profit is tax-free. This deduction applies once per year across all your overseas stock trades combined.

Taxable Base = Net Gain − 2,500,000 KRW

Step 5. Apply the 22% Tax Rate

Tax Owed = Taxable Base × 22% (national tax 20% + local income tax 2%)

④ The Exchange Rate Trap — Your KRW Return Isn't Your USD Return

Many investors overlook the impact of exchange rate fluctuations. A stock that gained in USD can show a loss in KRW if the dollar weakened, and vice versa. Since Korean tax law calculates gains in KRW, the exchange rate on each trade date directly affects your tax liability.

⑤ Tax-Loss Harvesting — Losses Are an Asset

If you hold positions with unrealized losses, selling them before year-end allows you to offset those losses against your gains — a strategy known as tax-loss harvesting. This is especially powerful in Q4 (October–December).

Korea does not have a "Wash Sale Rule" (unlike the US). You can sell a loss position and immediately buy it back — there is no 30-day waiting period. Just factor in transaction costs (spreads and commissions) when deciding whether it's worth it.

⑥ Dividend Tax — Handled Automatically, But Know the Rules

US stock dividends are subject to a 15% withholding tax at source, deducted automatically before the cash hits your account. Under the US-Korea tax treaty, this 15% rate equals or exceeds Korea's 14% dividend income tax (15.4% including local tax), so no additional Korean tax is owed on US dividends. Your brokerage handles this automatically — no action required.

⑦ Four Annual Tax-Saving Strategies

Strategy 1. Split Your 2.5M KRW Deduction Across Two Years

If you expect a 6 million KRW gain on a position, consider selling half by December 30 and the other half in January. Each year gets a 2.5M KRW deduction, potentially bringing your total tax to zero. This works best when you're confident in the stock's direction.

Strategy 2. Q4 Tax-Efficient Rebalancing

Review your portfolio in October or November. Identify losing positions and decide whether to harvest those losses before December 30.

Strategy 3. Track All Fees as Deductible Expenses

Every commission and fee on your trades is a deductible expense that reduces your taxable gain. Pull these from your brokerage transaction history and include them in your filing.

Strategy 4. Respect the T+1 Settlement Deadline

US stocks settle T+1. For a trade to count in the current tax year, it must settle by December 31. This means the trade must be executed by December 30. A December 31 trade settles January 2 — in the next tax year.

⑧ How to File on HomeTax — Every May

Capital gains from the prior year (January 1 – December 31) must be reported and paid between May 1 and May 31 of the following year. Late filing incurs a 20% non-filing penalty plus interest.

Method 1. Self-Filing on HomeTax (Free)

1. Go to hometax.go.kr and log in with your digital certificate
2. Navigate to: Tax Filing → Capital Gains Tax → Overseas Stocks
3. Enter each transaction: stock name, purchase date, sale date, cost basis (KRW), sale proceeds (KRW), fees
4. Review the calculated tax → Submit and pay

Method 2. Use Your Brokerage's Tax Service (Free)

Major Korean brokerages (Mirae Asset, Kiwoom, Samsung Securities, KB Securities, Korea Investment) offer free tax assistance services each May. They aggregate your trade history and often link directly to HomeTax for data transfer.

⑨ FAQ — Common Questions

Do I owe tax on stocks I haven't sold yet?

No. Korean capital gains tax applies only to realized gains from actual sales. Unrealized gains (paper profits) are not taxed.

My annual gain is under 2.5 million KRW — do I still need to file?

No filing obligation if your net overseas stock gain is 2.5 million KRW or less. However, if you have losses and want them on record (though they cannot be carried forward), you may optionally file.

Can I combine gains from US stocks and Japanese stocks for the 2.5M deduction?

Yes. All overseas stock gains and losses — regardless of country — are aggregated. The 2.5M KRW deduction applies to the net total once per year.

Is exchange rate profit taxed separately?

No separate currency gains tax applies. However, since tax is calculated in KRW, currency movements are already embedded in your computed gain or loss.

I had a large loss this year. Can I get a refund or carry it forward?

No. Overseas stock loss carryforward is not allowed in Korea. You can only offset losses against gains within the same calendar year.

⑩ Tax Calendar — Key Dates for Korean Retail Investors

※ This guide is for general informational purposes as of July 2026. Individual tax situations may vary. Consult a certified tax accountant (세무사) for personalized advice. Korean tax law is subject to annual revision.