South Korea taxes residents on worldwide income at progressive national rates of 6%–45%, plus a local income tax surcharge of 10% of the national tax. Foreign workers can elect a flat tax rate of 19% (plus 10% local surcharge = 20.9% total) instead of the progressive rates — this is typically beneficial for higher-income expats. The flat rate election is available for up to 20 years of Korean tax residency.
At a glance
Key Facts
Progressive Top Rate
45% national + 10% local surcharge = 49.5% combined
Flat Rate Option (Foreigners)
19% national + 10% local = 20.9% combined
Flat Rate Availability
Available for up to 20 years of Korean tax residency
Social Insurance (Employee)
~9% total (pension 4.5%, health 3.545%, employment 0.9%)
Tax Residency Trigger
183 days in Korea in a calendar year
Filing Deadline
May 31 (for prior calendar year)
Official Authority
National Tax Service (NTS)
Introduction
South Korea has emerged as a major expat destination — particularly in Seoul's finance and technology sectors — and its tax system offers a genuinely useful concession for foreign workers: the option to be taxed at a flat 19% national rate rather than progressive rates reaching 45%. For expats on higher salaries, this flat rate election can save tens of thousands of dollars annually compared to the standard progressive system.
This guide explains South Korea's tax structure for expats in 2026: how the progressive and flat rate systems compare, social insurance obligations, how residency is determined, and what US citizens living in South Korea need to file.
Section 01
South Korea's Progressive Income Tax Rates 2026
According to the National Tax Service (NTS), South Korea's national income tax uses eight progressive brackets:
Taxable Income (KRW)
National Tax Rate
Up to 14,000,000
6%
14,000,001–50,000,000
15%
50,000,001–88,000,000
24%
88,000,001–150,000,000
35%
150,000,001–300,000,000
38%
300,000,001–500,000,000
40%
500,000,001–1,000,000,000
42%
Above 1,000,000,000
45%
On top of national income tax, a local income tax (LIT) surcharge of 10% is applied — so the combined effective rates are 6.6% to 49.5%. At an income of 100,000,000 KRW (approximately $75,000 USD), the combined effective rate is approximately 25–28% after standard deductions.
Section 02
The Flat Tax Option for Foreign Workers
South Korea provides a significant benefit for qualifying foreign workers: the ability to elect a single flat tax rate of 19% on Korean-source employment income, rather than the progressive rates. With the 10% local income tax surcharge, the combined flat rate is 20.9%.
Who Qualifies
The flat tax election is available to foreigners who work in Korea under certain employment visa categories, including:
Those working for Korean companies or foreign company branches
Employees of foreign-invested companies
Certain technical or professional visa categories (E-series visas)
Duration
The flat rate election was available for 5 years originally, but has been extended to 20 years of continuous Korean tax residency. This is a substantial concession that differentiates Korea from many competing jurisdictions.
When Flat Rate Is Better Than Progressive
The flat rate (20.9% combined) is generally better than progressive rates for expats earning above approximately 70,000,000–80,000,000 KRW per year (~$53,000–60,000 USD). Below that income level, the progressive rates with standard deductions may produce a lower effective rate.
Key trade-off: under the flat rate, you cannot claim most standard deductions (earned income deduction, dependent deductions, education expenses, etc.). These deductions can significantly reduce progressive-rate liability at lower incomes.
Section 03
Social Insurance Contributions
South Korea has four mandatory social insurance schemes. Employee contributions in 2026 are approximately:
Scheme
Employee Rate
Employer Rate
National Pension (NPS)
4.5%
4.5%
National Health Insurance (NHIS)
3.545%
3.545%
Employment Insurance
0.9%
1.15–1.75%
Industrial Accident (Workers' Comp)
0%
Sector-based
Total employee contribution: approximately 8.945% of gross salary.
Health Insurance for Expats
From 2019, all registered foreign residents in Korea must enrol in the National Health Insurance Service (NHIS) — previously many expats maintained private insurance only. The NHIS covers a broad range of medical services at subsidised rates. The contribution is the same as Korean nationals: 3.545% employee, 3.545% employer.
Pension Totalization Agreements
Korea has pension totalization agreements with many countries (including the US), meaning expats may avoid double pension contributions. Under the Korea-US totalization agreement, workers covered by US Social Security continue paying US Social Security tax rather than the Korean National Pension. Confirm your specific situation with payroll or a tax adviser.
Section 04
Tax Residency in South Korea
South Korea determines tax residency on two criteria:
183-day rule: You spend 183 or more days in Korea in a calendar year (January–December)
Domicile test: You maintain a permanent place of abode or livelihood in Korea
Korean tax residents are taxed on worldwide income. Non-residents are taxed only on Korean-source income, at withholding rates (typically 20% for employment income, 22% with local surcharge).
Partial-Year Residency
If you arrive or depart Korea mid-year, you are treated as a resident for the portion of the year you spend in Korea (provided you meet the 183-day threshold). Employment income earned before arrival or after departure is not subject to Korean income tax.
Exit Requirements
When departing Korea permanently, you should: file a final income tax return, close any Korean bank accounts or report foreign assets, and deregister from the Alien Registration system. Failure to close out properly can create complications when re-entering Korea on a future visa.
Section 05
Filing Your Korean Income Tax Return
Korean income tax returns are filed annually with the National Tax Service. Employees have tax withheld at source (year-end settlement is performed in January for the prior year). The formal filing deadline is May 31.
Year-End Settlement (연말정산, Yeonmal Jeongsan)
Unlike many countries, Korea conducts a detailed year-end settlement process in January through the employer for salaried employees. Your employer collects documentation for deductions and credits, calculates the final liability, and adjusts your February payslip accordingly. Most employees do not need to file a separate return if their only income is employment income and the year-end settlement was completed correctly.
Situations requiring a personal return (5월 종합소득세 신고, May general income tax filing):
Business or freelance income alongside salary
Rental income
Foreign income not included in year-end settlement
Flat tax election by a foreign worker (sometimes requires separate NTS notification)
Section 06
US Citizens in South Korea
US citizens in South Korea must file US federal tax returns annually in addition to Korean obligations.
Form 1040: Required annually for all US citizens regardless of Korean residency
Flat tax interaction with US taxes: If you elect the Korean flat rate (20.9% combined), the Foreign Tax Credit provides less protection against US tax than if you paid Korean progressive rates. Depending on your income level, FEIE may be more beneficial.
Korea-US Tax Treaty: Provides relief from double taxation and contains tiebreaker provisions. The treaty reduces withholding on dividends, interest, and royalties.
FBAR: Required if Korean financial accounts exceed $10,000 aggregate
Korea-US Totalization Agreement: Prevents double Social Security / pension contributions — confirm your coverage certificate (Certificate of Coverage) situation before assuming you are exempt from Korean pension
The Korean flat tax election interacts in complex ways with your US Foreign Tax Credit strategy. Greenback's expat CPAs navigate both your Korean and US obligations — choosing the most tax-efficient approach for your income level.
⚠ Not the cheapest option — best for complex situations and expats who want a dedicated CPA.
Converting KRW salary to USD, GBP, or EUR? Wise transfers at the real exchange rate — significantly cheaper than Korean bank international transfers, especially for regular salary remittances.
⚠ For currency exchange only — not a bank account replacement.
What is the flat tax rate for foreigners in South Korea?
Foreign workers in South Korea can elect a flat national income tax rate of 19% instead of the progressive rates (6%–45%). Adding the 10% local income tax surcharge, the total combined rate is 20.9%. The election is available for up to 20 years of Korean tax residency. The downside: you cannot claim most standard deductions under the flat rate. The flat rate is generally beneficial for expats earning above approximately 70–80 million KRW per year.
Q
How does South Korea's local income tax surcharge work?
South Korea imposes a local income tax (LIT) of 10% on your national income tax liability. This is not 10% of income — it is 10% of the tax calculated. So if your national income tax is 5,000,000 KRW, the local income tax adds 500,000 KRW, for a total of 5,500,000 KRW. This applies to both the progressive rates and the flat tax election.
Q
Do I have to enrol in Korean national health insurance as an expat?
Yes. Since 2019, all registered foreign residents in South Korea must enrol in the National Health Insurance Service (NHIS). Contributions are 3.545% of gross salary (employee) with an equal employer contribution. NHIS provides broad coverage for medical services at subsidised rates. You cannot opt out in favour of private insurance only.
Q
When do I become a South Korean tax resident?
You become a South Korean tax resident if you spend 183 or more days in Korea in a calendar year, or if you maintain a permanent domicile (home or primary base of life) in Korea. Korean tax residents pay tax on worldwide income. Non-residents pay only on Korean-source income at withholding rates.
Q
What is the Korea year-end settlement (연말정산)?
Korea's year-end settlement (yeonmal jeongsan) is a January process where employers recalculate each employee's annual tax liability using actual deduction documentation — dependents, education costs, medical expenses, insurance premiums, and more. The difference from withheld tax is refunded or collected via the February payslip. Most salaried employees with only employment income do not need to file a separate annual return after this process.
Q
Do US citizens in Korea avoid double Social Security contributions?
Generally yes. The Korea-US Totalization Agreement means US citizens employed in Korea typically remain under US Social Security coverage and are exempt from Korean National Pension contributions. Your employer must obtain a Certificate of Coverage from the US Social Security Administration to confirm this. Do not assume exemption without documentation — the default without a certificate is that Korean NPS contributions apply.
Q
What is the filing deadline for Korean income tax?
The formal income tax filing deadline in South Korea is May 31 for the previous calendar year's income. However, salaried employees whose year-end settlement (연말정산) was correctly completed by their employer typically do not need to file a separate return. Those with additional income sources (freelance, rental, foreign income) must file by May 31 using the NTS online system (Hometax) or through a tax agent.
Disclaimer:This guide provides general information about South Korean taxation for expats for educational purposes only. Tax rules change frequently and individual circumstances vary significantly. Always verify current requirements with the National Tax Service (NTS) or a qualified Korean tax adviser. This is not tax advice.