Why Learn About Tax Before You Invest?
With US stocks, the tax events happen when you sell or when you receive dividends — not when you buy. Your after-tax return can differ significantly from the pre-tax chart. Frequent trading compounds this through transaction taxes and fees.
Tax-advantaged accounts (ISA, pension savings, IRP) follow different rules from a regular overseas brokerage account. See the ISA & Pension Guide for that comparison.
Where to Open an Account
Most Korean individual investors buy US stocks through the overseas trading service of a Korean domestic broker. Opening a US brokerage account directly (e.g., Interactive Brokers, Charles Schwab) is possible but adds complexity around international wire transfers, FATCA reporting, Korean tax treatment, and inheritance rules. For beginners, a domestic Korean broker is the standard starting point.
Spreading assets across too many brokerage accounts increases administrative burden. Consolidating transaction records in one place makes capital gains calculations significantly easier at year-end.
Brokers vary on commission rates, FX conversion spreads, fractional share support, and pre-market access. Zero-commission promotions often revert after an initial period. See the US Stock Basics Guide for an account-opening checklist.
Capital Gains Tax on US Stock Sales
For Korean residents, profits from selling overseas stocks are generally treated as capital gains. The annual basic deduction threshold reduces the taxable amount. Only the net profit above that threshold is taxed. The combined rate (including local surtax) has historically been around 22%, though exact figures depend on the applicable tax year and individual circumstances.
Illustrative Example (assumed rates — verify with current law)
Net profit for the year: ₩5,000,000. Basic deduction: ₩2,500,000. Taxable base: ₩2,500,000.
At ~22% combined rate → estimated tax: ~₩550,000. Actual result depends on your year, transactions, and account type.
If net profit is ₩2,000,000 (below the deduction threshold), capital gains tax may be near zero.
“No tax until you sell” is roughly true for capital gains. But dividends create a taxable event the moment they are paid — regardless of whether you reinvest them.
How Exchange Rates Affect Your Taxable Gain
Your taxable gain is calculated in Korean won, not dollars. If the USD/KRW rate rises while you hold a stock (weaker won), your won-denominated gain increases — even if the dollar price is unchanged. If the won strengthens, your reported gain shrinks.
Buy: $100 × ₩1,200/$ = ₩120,000 cost basis.
Sell: $100 × ₩1,400/$ = ₩140,000 → ₩20,000 gain even though the dollar price was unchanged.
See the USD/KRW Guide for more on currency effects. The exact exchange rate methodology used in tax calculations follows your brokerage and current tax law.
Dividend Withholding Tax
US companies and ETFs typically withhold a portion of dividends at source before crediting your account. Under the Korea-US tax treaty, the standard rate for Korean residents is commonly cited at 15%. Your brokerage statement will show “gross dividend / withholding tax / net credited.” Keep these records.
Example
Gross dividend: $100. Withholding at 15%: $15. Credited to account: $85.
In Korea, dividend income is also included in financial income. If your total interest + dividend income exceeds a certain threshold, comprehensive income taxation may apply.
REITs and some fund distributions may be taxed differently from ordinary dividends. Cross-reference your ETF prospectus with your brokerage's withholding statements. See the Dividend Guide for context.
Tax-Loss Harvesting — Use with Caution
Realizing a loss in the same calendar year can offset taxable gains in many cases. However, breaking up a solid long-term core position purely for a tax benefit may cost you more in missed compounding than you save. Tax strategy belongs with a tax professional; investment strategy belongs with your own plan.
Frequent realization of gains and losses also conflicts with the spirit of systematic investing — each round-trip adds transaction costs and potential tax friction.
Common Mistakes
Reporting from only one brokerage
If you use multiple brokers, you must aggregate. Omissions can trigger penalties.
Ignoring the KRW/USD conversion on gains
Your gain is taxed in won, not dollars. Currency moves affect your taxable amount.
Treating dividends as free money
Withholding tax plus potential domestic aggregation means net dividend is less than the headline yield.
Confusing ISA/pension and regular account rules
Tax exemptions, deductions, and capital gains treatment differ by account type.
Keeping only screenshots
Export year-end trade history and dividend PDFs from your broker for proper documentation.
Staying Ready for Tax Season
- Locate your broker's “overseas stock capital gains preview” menu at the start of each year.
- If you use multiple brokers, aggregate all records before filing — a single-broker view will be incomplete.
- Accounts under family members' names or minor children involve separate gift and name-lending considerations beyond this article's scope.
- Direct foreign brokerage accounts (US-based) may require additional FATCA and CRS disclosures.
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