Investing in Overseas Stocks from Korea: A Foreign Resident's Guide

Buying US, Hong Kong, Japanese, and European stocks through a Korean brokerage is operationally simple. You open the account, enable overseas trading, and you are in the same market as any other retail investor. The taxes and reporting are where the complexity lives, and where the rules are most underreported in English. Two things matter most for foreign residents: if you have been in Korea fewer than 5 years, you owe zero Korean capital gains tax on any overseas stock gain. And a portfolio large enough to pay US$20,000-plus in annual dividends will trigger a ₩20M comprehensive-tax trap that converts your flat 15.4% rate into something much worse. The hub guide on personal finance accounts established the headline rules. This guide covers the operational detail: the 5-year clock mechanics, the annual filing process, dividends by country, the ₩20M trap, the ₩500M reporting form, FX, and the full US-person picture on PFIC, FBAR, and Form 8938.

The 5-year residency exemption

What the law says

Under Income Tax Act Article 118조의2 (소득세법 제118조의2), a Korean resident who has maintained a Korean address or place of residence continuously for 5 or more years as of the date of sale is subject to Korean capital gains tax (양도소득세) on overseas stock gains. The inverse: if you have not reached that 5-year threshold at the sale date, you owe nothing. The NTS overseas stocks page confirms this directly. There is no cap on the exemption. A US$2M gain realized in year 4 of Korean residence is zero-tax.

The clock runs to each individual sale date, not to the calendar year end. If you reach your 5-year anniversary in October, gains on shares sold before October that year are exempt. Gains on shares sold from October onward in that same year are taxable.

What "continuous" (계속) means in practice

The statute uses the word 계속 (continuous), and this is where most English coverage stops. The practical question is: what breaks the clock?

Under Enforcement Decree Article 4 (소득세법 시행령 제4조), clearly temporary absences do not break continuity. The decree specifies that if the purpose of departure is obviously temporary, such as tourism or medical treatment, and you return to Korea, the period abroad is treated as continued Korean residence. The factual indicators are: your family's residential location, the location of your domestic assets, and the stated purpose of travel.

Short holidays and business trips do not break the clock if your life base remains in Korea. An extended departure where you have moved family abroad, vacated your apartment, and made no return plan would likely break continuity.

One Korean tax industry source (일간NTN) interprets the decree to mean that a roughly 3-month absence for temporary purposes does not reset the clock. This reading is consistent with the 시행령 제4조 framework, but the NTS has not published a formal ruling with a specific permitted-absence day count. There is no NTS bright-line rule stating that absences under 90 days are automatically safe. The determination is factual, not formulaic.

If your residency situation is at all borderline, including extended absences, family temporarily abroad, or long-haul secondments, consult a Korean tax agent (세무사) before making any significant overseas stock sales.

ARC cancellation and re-registration

No NTS primary ruling specifically addresses whether cancelling your ARC upon departure and re-registering upon return resets the 5-year clock. The most supportable inference from the statutory language is that the 5-year test measures actual continuity of Korean residence, not the administrative status of your ARC. A short gap that was genuinely temporary in character likely preserves continuity; a gap that constituted a real end of Korean residence likely resets it. Do not treat your ARC registration dates as a substitute for the factual residency analysis.

Multiple residency stints

The word 계속 (continuous) points toward a single unbroken stretch. A foreign resident who lived in Korea for 3 years (2018 to 2021), then left and returned in 2024, most likely needs a fresh 5 years from the 2024 return date. No NTS ruling specifically confirms this for the multi-stint scenario. Treat it as the most reasonable statutory reading and verify with a tax agent if your situation involves a gap.

Planning for year 5

If you are approaching your 5-year anniversary and hold significant unrealized gains in overseas stocks, the timing of sales is a real decision. A sale completed before you cross the threshold is potentially exempt. A sale completed after costs up to 22% in Korean tax above the ₩2.5M deduction. Whether to realize gains before crossing the threshold is worth a conversation with a Korean tax agent.

After 5 years: the 22% CGT regime

The rate and deduction

Once you cross the 5-year threshold, all overseas stock gains are taxable in Korea at 22%: 20% national capital gains tax (양도소득세) plus a 2% local income tax surcharge (지방소득세, equal to 10% of the national tax). This applies to net gains above the annual ₩2.5M basic deduction (양도소득 기본공제).

The ₩2.5M deduction is one per person per year, shared across taxable domestic and overseas stock gains combined. It is not ₩2.5M per account or per asset class.

Loss netting and no carryforward

Losses on overseas stocks can be offset against gains from other overseas stock sales within the same tax year. Since 2020, gains and losses from taxable domestic Korean stocks can also be netted against overseas stock gains. This gives you some flexibility to harvest losses inside a calendar year.

One limit applies: losses on domestic Korean stocks that are not themselves subject to Korean CGT (for example, retail investor positions below the large-shareholder threshold) cannot be used to offset overseas gains.

There is no carryforward. Losses in excess of gains in a given year are extinguished. You cannot apply this year's loss to reduce next year's tax.

No withholding at sale

Korean brokerages do not withhold at the point of sale. The full tax liability is deferred to the May annual filing. This means you receive full proceeds at sale and need to budget for the tax bill yourself by the filing deadline.

The annual filing: step by step

This section assumes you have crossed the 5-year threshold and realized taxable gains in the prior calendar year.

Step 1: Get your broker's year-end summary (January or February). Each Korean brokerage produces an overseas stock capital gains data file (해외주식 양도소득세 자료) for the prior calendar year. Download it from your brokerage's trading platform or app. It lists each trade, proceeds, acquisition cost, FX rate applied, and net gain or loss per position. If you use multiple Korean brokerages, download a file from each.

Step 2: Aggregate across all accounts. Add up gains and losses from all Korean brokerage accounts. If you also hold accounts at foreign-domiciled brokers (Interactive Brokers, Charles Schwab, etc.), those gains are equally subject to Korean CGT once you are past 5 years. Obtain trade confirmations from those accounts separately and include them.

Step 3: Apply the ₩2.5M annual deduction. Subtract ₩2.5M from your combined net gain. If your net gain is ₩2.5M or less, your tax is zero. Keep records regardless.

Step 4: Calculate the tax. Multiply net gain above ₩2.5M by 22%. Apply any foreign tax credit (외국납부세액공제) for source-country capital gains taxes withheld at sale (rare for US, HK, UK, Japan, Germany).

Step 5: File at Hometax (홈택스), 1 to 31 May. Log in at hometax.go.kr using your certificate or simple authentication (공동인증서, 금융인증서, or 간편인증). Path: Tax Return (신고/납부) → Capital Gains Tax (양도소득세) → Overseas Stocks (해외주식). Enter total sale proceeds (양도가액), acquisition cost (취득가액), and commissions (필요경비). Upload your broker's data file as supporting documentation. The system calculates the tax.

In the taxpayer fields, enter your full English name as it appears in your passport and your foreign resident registration number from your ARC. If you do not have an ARC number, use your passport number.

Step 6: Pay by 31 May. Pay electronically by bank transfer, virtual account (가상계좌), or at a tax office. The Korea Investment and Securities Hometax filing guide shows the complete screen-by-screen path for the 2024 filing year.

Documents to keep for 5 years: your brokerage's gains data file, trade confirmations, and any foreign tax payment receipts if claiming a credit.

Dividends: what gets withheld and where

When you hold overseas stocks, the source country withholds a portion of each dividend before it reaches your Korean brokerage account. The rate depends on the bilateral tax treaty between Korea and the source country. The numbers below are the treaty caps that apply to dividends paid TO a Korean resident. Some countries withhold at their full domestic rate first and require you to file a refund claim to recover the difference down to the treaty cap.

Treaty caps on dividends paid to a Korean resident (as of 2026)

Direction matters: the rates above are what is withheld at source on dividends paid to you as a Korean resident. They are different from the Korean withholding rates that apply when a Korean company pays a dividend to a non-resident foreign holder. Verify against the source country's tax authority and the specific bilateral treaty article on portfolio dividends before relying on a rate for filing. For US dividends, IRS Publication 901 is the authoritative cross-reference.

The W-8BEN for US stocks

Without a W-8BEN on file, the US paying agent defaults to 30% withholding. Korean brokerages submit the W-8BEN on your behalf when you activate US stock trading. It must be renewed every 3 years. If your W-8BEN has lapsed or was never submitted, dividends from US holdings are taxed at 30% instead of 15%. Confirm the status of your W-8BEN with your broker.

How dividends are taxed in Korea

For most foreign residents, dividends from overseas stocks are subject to the standard Korean financial income rate of 15.4% (14% national plus 1.4% local). Korean brokerages handle this withholding on dividends credited to your account.

Where the source country already withheld tax on the dividend, the Korean foreign tax credit (외국납부세액공제) offsets the duplicate taxation. For US dividends, the 15% US withholding broadly offsets the 14% Korean rate, leaving a small residual Korean liability, assuming your total financial income stays below ₩20M. The exact net depends on your comprehensive income and whether the ₩20M threshold is crossed.

The ₩20M financial income trap

This is the most underreported issue for foreign residents with meaningful investment portfolios. Read this section even if you are under 5 years and exempt from CGT.

How the threshold works

All interest and dividend income from all sources combined counts as financial income (이자·배당소득). When your total financial income for the calendar year exceeds ₩20M, 금융소득종합과세 (financial income comprehensive taxation) applies. The flat 15.4% withholding rate is replaced. All financial income is stacked on top of your other income (salary, business income, etc.) and taxed at progressive rates of 6% to 45%.

The first ₩20M retains a floor rate of 14% under the Income Tax Act (소득세법 제62조), but the marginal rate on income above ₩20M can reach 45% for high earners.

Foreign dividends count at gross, before source-country withholding. If you received US$20,000 in US dividends and the US withheld 15%, leaving you with US$17,000, the Korean ₩20M threshold is calculated on the gross US$20,000, not the net US$17,000. This is confirmed by NTS call center guidance and established Korean tax practice.

A plain-numbers example

A foreign resident holds US$500,000 in US dividend-paying stocks at a 4% annual yield. That produces US$20,000 in gross dividends per year, approximately ₩27M at ₩1,350 per dollar. That alone exceeds ₩20M and triggers comprehensive taxation.

Add any Korean bank interest, domestic Korean dividends, or other financial income and the ₩20M threshold is crossed at a smaller portfolio size.

The ISA consequence

Crossing the ₩20M threshold in a given year blocks ISA enrollment for the next 3 years. If you are classified as a 금융소득종합과세 대상자 (financial income comprehensive taxation subject), you cannot open a new ISA until 3 years have passed. This is noted in the hub guide and confirmed by FSC ISA eligibility rules.

Practical mitigations

Prefer growth-oriented stocks over high-dividend stocks if your dividend income is approaching ₩20M. Use the ISA wrapper for Korean dividend-paying assets within the ISA contribution caps, since gains inside an ISA are netted and taxed at 9.9% at most, not counted toward the ₩20M threshold. If you hold dividend payers in a Roth IRA or other tax-deferred account in your home country, keep them there rather than shifting them into a Korean account.

The ₩500M overseas financial account report

What triggers it

If the combined balance of all your accounts at foreign-domiciled financial institutions exceeds ₩500M on any single month-end during the calendar year, you must file an overseas financial account report (해외금융계좌 신고서, 별지 제45호) with the NTS. The trigger is any one of the 12 month-end snapshots in the year, not an annual average and not a year-end balance only.

The form name is 해외금융계좌 신고서 (별지 제45호), filed under the Act on Coordination of International Tax Affairs (국제조세조정에 관한 법률). File at Hometax between 1 June and 30 June of the following year.

What counts, and what does not

Accounts that count toward ₩500M:

• Foreign bank accounts (Chase, HSBC, Citibank, etc.)
• Foreign brokerage accounts (Charles Schwab, Interactive Brokers, Fidelity, etc.)
• Foreign insurance and investment products
• Foreign virtual asset accounts (Binance, Coinbase, etc.)

Accounts that do not count:

• Korean brokerage accounts, even when the holdings inside are US or other foreign stocks. A Mirae Asset, Samsung Securities, or Kiwoom account holding Apple, Tesla, or any other overseas security is at a Korean financial institution and is not a foreign account.
• Korean bank accounts (Shinhan, KB, Kakao Bank, etc.)
• Korean IRP, ISA, or pension savings accounts

For the large majority of foreign residents who buy overseas stocks exclusively through Korean brokerages, the ₩500M rule does not apply. It becomes relevant if you maintain a Schwab, IBKR, or other foreign-domiciled account with a significant balance.

The foreign-resident exemption

Foreign residents whose cumulative Korean residence in the 10 years before the reporting year-end totals 5 years or fewer are exempt from this obligation. This is a cumulative test, not a continuous one: two separate 2.5-year stays in the past decade add up to 5 cumulative years. The exact statutory language confirmed by NTS: "신고대상 연도 종료일 10년 전부터 국내에 주소나 거소를 둔 기간의 합계가 5년 이하인 자" (a person whose cumulative domestic residence in the 10 years before the reporting year-end is 5 years or less).

Penalties

Late or non-filing carries a 10% penalty on the unreported amount, up to ₩1B. False reporting carries an additional 10%.

FX mechanics

Two ways to place overseas stock orders

Korean brokerages let you choose how FX is handled.

KRW-denominated order (원화주문): You place the order in Korean won. The brokerage executes the trade in the foreign currency and converts overnight at its posted spread, typically 0.5% to 2% depending on the provider and time of day. No pre-conversion is needed. The risk is overnight FX movement: if the exchange rate moves unfavorably before the conversion completes, you may face a currency shortfall requiring additional deposit.

FX order (환전주문): You first convert Korean won to US dollars (or other currency) and hold the balance as a foreign currency deposit (외화예수금) in the brokerage account. You then buy and sell stocks in dollars, with proceeds returning to the dollar balance. Buying another US stock does not require converting back to Korean won each time. This saves significantly on FX costs for active overseas traders. The unified margin service (통합증거금) is the feature name at major brokerages for this dollar-holding functionality.

FX spreads (as of 2026, verify with your broker before converting)

Indicative rates only. Promotional spreads change frequently.

• Samsung Securities: approximately 0.05% mark-up on the standard rate for USD
• Mirae Asset Securities: approximately KRW 5 per dollar for USD; 0.5% for other currencies
• Toss Securities: approximately 95% discount off the standard spread during regular hours; 50% off-hours
• KB Securities: approximately 1% standard; waived under the KB Global OneMarket service

Source: hohopress.com 2026 brokerage comparison.

For large single transfers, a bank wire at the interbank rate often beats the brokerage's spread. Compare before converting.

FX and your tax calculation

Tax is always calculated in Korean won. The rate used is the first-published standard exchange rate (최초 고시 기준환율) of the business day.

For each trade, the rules are:

• Acquisition cost: base rate on the fund withdrawal date (when you sent KRW to the brokerage to buy)
• Sale proceeds: base rate on the fund deposit date (when sale proceeds settled in your account)

A US$10,000 gain in dollar terms may produce a different won gain depending on the exchange rate between the purchase date and the sale date. If the dollar strengthened during your holding period, your Korean won gain will be larger than the dollar gain suggests, and vice versa. This affects both the ₩2.5M deduction and the 22% tax calculation. Your brokerage's year-end data file applies these rates automatically, but verify the figures before filing.

The US-person section: PFIC, FBAR, and Form 8938

This section applies only to US citizens, US permanent residents (green card holders), and certain other US tax residents. Other readers can skip ahead to the next section.

PFIC: the Korean ETF problem

A Passive Foreign Investment Company (PFIC) is a foreign corporation where 75% or more of gross income is passive (dividends, interest, capital gains), or where 50% or more of average assets produce passive income. The tests are applied each tax year. The statutory basis is IRC Section 1297.

Korean ETFs are PFICs. KODEX 200, TIGER S&P500, KBSTAR, ACE, and similar Korean collective investment funds invest in portfolios of stocks and earn passive income from them. They almost certainly satisfy both the income test and the asset test. This is the consistent position of US tax practitioners working with American residents in Korea, based on first-principles application of IRC Section 1297 to the structure of Korean 집합투자기구 (collective investment vehicles). No formal IRS ruling naming specific Korean ETFs as PFICs has been published, but the structural analysis is clear.

Individual Korean operating-company stocks are not PFICs. Samsung Electronics, NAVER, Kakao, Hyundai Motor, SK Hynix, and similar listed operating companies are not PFICs. They are active businesses whose income is predominantly non-passive. Holding individual Korean stocks does not create a PFIC obligation.

Korean bank deposits are not PFICs. A savings account or CD at a Korean bank is a debt instrument, not equity in a corporation.

The three PFIC regimes

Without making an election, the default Section 1291 excess distribution regime applies. Any gain on sale or excess distribution is taxed at the highest ordinary income rate (currently 37%) plus an IRS interest charge running back to the year you first held the PFIC. This is the most punitive outcome.

The Qualified Electing Fund (QEF) election is functionally unavailable for Korean ETFs. The QEF election requires the fund to issue a PFIC Annual Information Statement each year. Korean fund managers do not produce this document.

The Mark-to-Market (MTM) election is likely available for Korean ETFs, since KRX is a qualified exchange and Korean ETFs trade on it daily (satisfying the marketable stock requirement of at least 15 days per quarter). Under MTM, you recognize annual gains as ordinary income and annual losses against prior MTM gains. This eliminates the punitive interest charge but does not preserve capital gains character. File Form 8621 for each PFIC per year to make and maintain the election.

The ISA and IRP wrappers do not shield PFIC treatment. US tax law looks through the Korean account structure. Korean ISA tax benefits and IRP tax deferral are not recognized by the IRS. If your ISA holds KODEX or TIGER ETFs, those holdings are PFICs in the eyes of the IRS regardless of the ISA wrapper.

Practical guidance for US persons

Hold individual Korean operating-company stocks rather than Korean ETFs for direct Korean equity exposure. For broad Korea market exposure, use a US-domiciled ETF such as iShares MSCI South Korea ETF (EWY) listed on NYSE. EWY is not a PFIC because it is a US-domiciled fund. If you already hold Korean ETFs inside a Korean brokerage, ISA, or IRP, consult a US tax professional about whether to unwind the positions or make the MTM election. File Form 8621 for each PFIC you hold, per year, regardless of whether a distribution or sale occurred (unless the small PFIC exception under Section 1298(f) applies: aggregate PFIC value under US$25,000 for single filers or US$50,000 joint, with no distributions or dispositions; verify current thresholds with your tax preparer).

FBAR: FinCEN Form 114

File FBAR if the aggregate value of all foreign financial accounts exceeded US$10,000 at any point during the year. Even one day above US$10,000 triggers the obligation.

What counts as a foreign financial account for FBAR:

• Korean bank accounts (Shinhan, KB, Kakao Bank, Toss Bank, etc.)
• Korean brokerage accounts (Mirae Asset, Samsung Securities, Kiwoom, etc.)
• Korean ISA accounts
• Korean IRP accounts: the FBAR regulations exempt domestic US retirement accounts described under IRC Sections 408 and 408A. Korean IRP is not described in those provisions. The prevailing position among US tax practitioners is that Korean IRP is FBAR-reportable as a foreign financial account. No formal IRS ruling specifically addressing Korean IRP has been published. Confirm with a US tax professional.
• Korean pension savings accounts (연금저축): same analysis as IRP, likely reportable.
• Foreign virtual asset accounts at non-US platforms

FBAR is filed separately from your US tax return, by 15 April with an automatic extension to 15 October. File electronically via the FinCEN BSA E-Filing system.

Penalties are severe. Non-willful violations can reach US$16,536 per violation (2025 inflation-adjusted). Willful violations: greater of US$165,353 or 50% of the account balance. Criminal penalties apply for the most serious cases.

Form 8938: FATCA

Form 8938 (Statement of Specified Foreign Financial Assets) is filed with your annual US tax return. For Americans living abroad, the filing thresholds are:

Form 8938 covers more than financial accounts. It also covers directly held foreign stocks, interests in foreign entities, and foreign pensions and deferred compensation plans. Korean IRP and pension savings (연금저축) are likely reportable as foreign pension or deferred compensation plans, subject to the thresholds above. The IRS Form 8938 Q&A confirms that foreign pension plans are reportable.

Filing Form 8938 does not satisfy the FBAR obligation, and filing FBAR does not satisfy Form 8938. Both filings may be required for the same accounts. The penalty for not filing Form 8938 starts at US$10,000 and increases by US$10,000 per 30 days after IRS notification (capped at US$50,000), plus a 40% accuracy penalty on understatements from undisclosed assets.

Status changes: entering and leaving Korean residency

Arriving mid-year

Your 5-year CGT exemption clock starts from the date you established Korean tax residency, not from 1 January of your arrival year. If you arrived in October 2024, your clock runs from October 2024. You would need to reach October 2029 before any overseas stock sales are subject to Korean CGT.

If you arrive and sell overseas stocks in the same calendar year, only sales made after your residency was established are analyzed against the 5-year clock. Sales made before you became a Korean resident are not within Korean CGT jurisdiction at all.

Departing Korea

Once you cease to be a Korean tax resident (거주자), gains on overseas stock sales made after that date are not subject to Korean CGT. Your residency ends when you vacate your Korean residence, deregister your ARC, and depart. Gains realized before that transition date remain taxable and must be filed by the normal 31 May deadline.

If you crossed the 5-year threshold before departing, consider the timing of any large overseas stock sales carefully. Selling after you are no longer a 거주자 puts the gain outside Korean tax jurisdiction entirely.

Departure tax

Korea's departure tax (국외전출자 양도소득세) applies to large shareholders (대주주) with 1% or more of a listed company, departing Korea after 5 or more years of Korean residence. It applies to unrealized gains in domestic Korean stocks only, not overseas stocks. A typical retail foreign investor with a diversified portfolio of overseas securities is not within its scope. If you hold any significant stakes in Korean-listed companies, verify your status at the NTS departure tax page before departing.

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FAQ

I just moved to Korea this year. Do I owe Korean tax on US stocks I sell?

No. If you have lived in Korea for fewer than 5 consecutive years as of the date you sell, you owe zero Korean capital gains tax on overseas stock gains, regardless of the amount. The exemption is confirmed by the NTS overseas stocks page (소득세법 제118조의2). You have no annual reporting obligation while within the exemption period. Your 5-year clock started from the date you established Korean residence.

When does my 5-year clock start?

Your clock starts from the date you established Korean tax residency, not the date you first arrived as a visitor or tourist. For most foreign residents this is the date your ARC was issued and you began residing in Korea continuously. The test is the sale date versus your 5-year anniversary: sell before that date and you pay zero; sell after and the 22% rate applies above ₩2.5M.

Do my Korean brokerage holdings count toward the ₩500M overseas reporting threshold?

No. The reporting obligation covers accounts at foreign-domiciled financial institutions only. A Mirae Asset or Samsung Securities account holding Apple, Microsoft, or any other foreign stock is at a Korean institution and does not count toward ₩500M. Only accounts at institutions like Charles Schwab, Interactive Brokers, or overseas banks count. If all your overseas stocks are held through a Korean brokerage, you likely have no reporting obligation under this rule.

I have a US$300K portfolio of US dividend stocks. Am I going to hit the ₩20M comprehensive-tax threshold?

At a 4% dividend yield, a US$300K portfolio produces roughly US$12,000 in annual dividends, approximately ₩16M at current rates. That sits below the ₩20M threshold on its own. But add Korean bank interest, domestic dividends, or any other financial income and the combined total can cross ₩20M. The threshold is measured on all interest and dividend income combined, with foreign dividends counted at gross before any source-country withholding. If you are approaching ₩20M in total financial income, consult a Korean tax agent (세무사) before year-end.

I am a US citizen. Can I buy KODEX 미국S&P500 inside my ISA?

You can open the ISA and buy the ETF under Korean rules. The problem is US tax law. KODEX 미국S&P500 is a Korean ETF and almost certainly a PFIC under IRC Section 1297. The ISA wrapper provides no US tax shield: the IRS looks through the Korean account structure. Without an election, the punitive default excess-distribution regime applies. The mark-to-market (MTM) election is likely available since KODEX trades on KRX, but it converts gains to ordinary income. For Korea S&P500 exposure without PFIC complications, use a US-domiciled ETF like iShares MSCI South Korea (EWY) listed on NYSE, or hold individual Korean operating-company stocks directly. Verify your specific situation with a US tax professional.

What is the cheapest way to convert KRW to USD for overseas stock purchases?

Korean brokerages offer two methods. The KRW-denominated order (원화주문) converts automatically at the brokerage's spread, typically 0.5% to 1.5% one-way at most providers. The direct FX order (환전주문) lets you pre-convert KRW to USD and hold the dollars as a foreign currency deposit (외화예수금) inside the brokerage. For active USD traders, holding USD in the account and buying without re-converting each time saves significantly on round-trip FX costs. For large single transfers, a separate bank wire at the interbank rate can beat the brokerage spread. Check current rates directly with your broker before converting, as promotional rates change frequently.

If I leave Korea, do I still owe Korean tax on overseas stock gains I realize after I leave?

No. Once you are no longer a Korean tax resident (거주자), Korea does not tax your overseas stock gains. If you vacate your apartment, deregister your ARC, and depart Korea, gains you realize after that date are not subject to Korean CGT. Any gains realized while you were still a 거주자 remain taxable and must be filed by the normal 31 May deadline. If you crossed the 5-year threshold before departing, consider the timing of your final overseas stock sales carefully: selling before you cease to be a 거주자 is taxable; selling after is not.

Will Korea charge a departure tax on my US stocks?

Almost certainly no, for a typical retail investor. Korea's departure tax (국외전출자 양도소득세) applies only to 대주주 (large shareholders) with 1% or more of a listed Korean company, and it covers Korean domestic stocks only, not overseas stocks. Foreign residents whose holdings consist of US, HK, or Japanese stocks held through a Korean brokerage are not within the scope of the departure tax. Confirm at the NTS departure tax page if you hold any significant Korean domestic positions.

@misc{seoulstart-overseas-stocks-korea-foreign-residents,
  author = {{Seoulstart Editorial Team}},
  title = {{Investing in Overseas Stocks from Korea: A Foreign Resident's Guide (2026)}},
  year = {2026},
  publisher = {Seoulstart},
  url = {https://seoulstart.com/guides/overseas-stocks-korea-foreign-residents},
  note = {Last updated May 25, 2026}
}