Korea Income Tax for Foreign Residents: May Filing Window (종합소득세)

The comprehensive income tax return (종합소득세 신고) for the previous calendar year is normally filed May 1 through May 31. If May 31 falls on a weekend or public holiday, the due date moves to the next business day. For 2025 income, the NTS filing deadline was June 1, 2026 because May 31 fell on Sunday. If you have any income beyond employer-handled salary (freelance, rental, investments, side work), file via Hometax. Jump to filing instructions.

If your only Korean income is a salary from a Korean employer, your company handles most of the paperwork. If you have any other income, you are responsible for filing during the May window. Missing the deadline can result in penalties.

Korea has a progressive income tax system with rates from 6% to 45%. Foreign residents working in Korea are generally subject to the same tax rules as Korean nationals, with some important exceptions and options that can reduce your tax bill.

Tax residency: You are a Korean tax resident if you have a domicile (주소) in Korea or a place of residence (거소) in Korea for at least 183 days. Residents can be taxed on worldwide income. Non-residents are taxed only on Korea-source income.

Korean income tax rates (verify current brackets at www.nts.go.kr):

Local income surtax (지방소득세) adds an additional 10% of income tax liability.

Rates and brackets shown apply to tax year 2025. The 2025-income comprehensive return was due June 1, 2026 because May 31 fell on Sunday. Confirm the current year's brackets at the NTS, and use the NTS year-end settlement calculator to estimate your own liability.

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The foreigner flat rate: 19%

Eligible foreign employees in Korea can elect a flat 19% tax rate on employment income instead of the progressive 6–45% brackets. The flat rate is usually worth testing only at higher incomes and when you have few deductions, because the election gives up ordinary deductions and credits. The actual breakeven depends on the personal deductions and credits you claim (rent credit, credit-card deduction, family deductions), so run the numbers for your own situation. The election is governed by 조세특례제한법 Article 18-2.

The election lasts 20 years from your first day of work in Korea (extended from 5 years in the 2023 tax reform). Workers who first begin employment in Korea on or before December 31, 2026 are eligible. This sunset date has been pushed back in past tax reform cycles and may be extended again, so if your start date is close to it, confirm the current cutoff with your employer's HR department or a Korean tax accountant (세무사).

How to elect the flat rate:

• At year-end settlement (연말정산), your employer's payroll department will ask if you want to use the flat rate
• The flat rate is usually worth testing only for higher earners with limited deductions; run both methods before choosing
• If you're unsure, ask your employer's HR or accounting team

The flat rate applies to employment income only. Other income (freelance, rental, investments) is taxed at progressive rates.

Not sure which tax credits and refunds apply to your situation? Run the Benefits Checker for a quick eligibility list across rent tax credit, credit-card deduction, freelancer 3.3% refund, and the flat-tax election, all based on your visa and income band.

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Year-end tax settlement (연말정산)

If you're employed by a Korean company, your employer handles most of your tax administration through year-end settlement (연말정산) in January–February for the previous calendar year. This is separate from the comprehensive income tax filing (종합소득세). See below.

What happens:

1. Your employer compiles all your salary payments and tax withholdings for the year
2. They calculate whether too much or too little tax was withheld
3. You receive a refund or pay additional tax in February/March
4. Your employer files the settlement receipt with the NTS by March 10

What you need to provide:

• Receipts for deductible expenses (medical bills, education, donations)
• Proof of dependents if applicable
• Your choice of flat rate vs. progressive rate

Most employers' HR departments will guide foreign employees through this. Ask your HR team in December if you're unsure what to expect.

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Filing your own tax return

If you have income beyond employment (freelance work, rental income, dividends, side business income), you must file a comprehensive income tax return (종합소득세 신고) during the May filing window for the previous calendar year.

How to file:

1. Visit Hometax (www.hometax.go.kr), the NTS online filing portal
2. Log in with an available authentication method
3. Enter all income and deductions
4. Submit and pay any balance due

Hometax is the official NTS online filing portal. Consider hiring a Korean accountant (세무사) for your first year if your situation is complex.

Missing the filing deadline carries a non-filing penalty of 20% of the tax due (rising to 40% for deliberately concealed income), plus a daily late-payment charge of 22/100,000 of the unpaid tax. File on time to avoid both.

NTS foreigner services: The National Tax Service has a dedicated foreigner assistance line: 1588-0560 (English available).

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Double taxation treaties

Korea publishes tax treaty information through MOEF. These treaties can prevent the same income from being taxed twice, assign taxing rights for different income types, and allow foreign tax credits so Korean tax paid reduces your home country liability.

What treaties typically do:

• Prevent the same income from being taxed twice (once in Korea, once in your home country)
• Specify which country has taxing rights on different types of income
• Allow foreign tax credits: taxes paid in Korea reduce your home country tax liability

US citizens and green card holders: The US has its own worldwide-income filing rules for citizens and green card holders abroad. Korean tax treaties and credits do not remove the need to check US filing duties. Use a US-Korea cross-border tax specialist if this applies to you.

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Before leaving Korea: what to do

Departing foreign residents should close out Korean tax items before flying: file a final income tax return if any income for the year is unreported, get withholding certificates from the employer, and appoint a tax manager if Korean tax matters will continue after departure.

1. File a final income tax return if required

If you have taxable income for the year you're leaving and you're leaving mid-year, settle your taxes before departure. Your employer will handle your employment income; report any other income to the NTS. If you will have ongoing Korean tax matters after you leave, you can also appoint a tax manager (납세관리인) through the pre-departure tax manager registration (출국 전 납세관리인 신고), which is a separate filing from the return.

2. Get employer tax certificates

Ask for your earned income withholding certificate (근로소득 원천징수영수증), retirement income withholding certificate if you received severance, and the payment statement (지급명세서) filed with the NTS. These documents make later correction or refund claims much easier.

3. Appoint a tax manager if Korean matters continue

If you will have ongoing Korean tax matters after departure, file a tax manager appointment (납세관리인 신고). This is separate from filing the return itself.

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Useful resources

Korean tax administration for foreign residents runs through three main channels: the National Tax Service (NTS) foreigner assistance line at 1588-0560 with English support, the Hometax (홈택스) online filing portal at www.hometax.go.kr, and the Ministry of Economy and Finance tax-treaty search at www.moef.go.kr. US citizens generally need a US-Korea cross-border specialist on top.

• National Tax Service (NTS) foreigner line: 1588-0560 (English available)
• NTS Hometax: www.hometax.go.kr
• Tax treaty search: mofe.go.kr: Tax information: Tax treaties
• US citizens: use a US-Korea cross-border tax specialist

@misc{seoulstart-korea-foreign-resident-tax-guide,
  author = {{Seoulstart Editorial Team}},
  title = {{Korea Income Tax for Foreign Residents: May Filing Window (종합소득세)}},
  year = {2026},
  publisher = {Seoulstart},
  url = {https://seoulstart.com/guides/korea-foreign-resident-tax-guide},
  note = {Last updated June 5, 2026}
}