About this guide
Who should file a return?
A foreign resident with global income in the relevant year has to file a tax return to the head of the competent district tax office in the same way as a Korean resident. A non-resident who has a business place in Korea (a “permanent establishment” in tax-treaty terms) or real-estate income from Korean sources is also obligated to file and pay global income tax for domestic-source income.
Income tax is imposed on an individual's income on an annual basis. Income is classified into global income, retirement income and capital gains; global income means interest income, dividend income, business income, wage & salary income, pension income and other income.
Residents who may choose not to file a finalized return (Income Tax Act art. 73)
- Only wage & salary income
- Only retirement income
- Only public pension income
- Only business income subject to year-end settlement
- Only religious persons' income (other income) subject to withholding
- Only wage & salary income and retirement income
- Only retirement income and public pension income
- Only retirement income and the business income in (4)
- Only retirement income and the religious persons' income in (5)
- Only interest, dividend, pension or other income subject to separate taxation
- Falls under (1)–(9) and additionally has only separately-taxed interest, dividend, pension or other income
- No additional income after an occasional imposition
When is the deadline for 2025?
The taxable period for income tax is one year, from Jan. 1 to Dec. 31. The filing period is May 1 to May 31 of the following year; when the last day falls on a Saturday, Sunday or public holiday, the next business day is the deadline. The due date for the 2025 return is therefore June 1, 2026. Businesses that submit a report certifying compliant filing have until June 30.
Special deadlines
- Death of a resident: six months from the last day of the month in which the first day of inheritance (date of death) falls.
- Departure to move overseas (a resident becoming a non-resident): the taxable period is Jan. 1 to the date of departure, and the return is due the day before departure. If you leave between Jan. 1 and May 31, you must also file the previous year's return before departure.
Which form, and what documents?
There are four return forms — attached Form 40 (1) (general cases and self-assessment), Form 40 (4) (business income under the simplified expense rate filed by estimation, or wage/pension/other income, or two or more income types), Form 40 (5) (religious persons' income only) and Form 40 (6) (income subject to separate taxation). English versions: nts.go.kr/english → Resources → Forms.
Documents generally attached to the return
- Copy of the alien registration card issued by the local immigration office
- Application forms for tax deductions, credits and reduction/exemption, plus certifying documents
- Documents needed to calculate gross revenue and necessary expenses — and, where there is business income, the balance sheet, income statement, compound trial balance with attachments, and statement of adjustment
- Other documents the tax authority may request under the Income Tax Act
Keep your records
Alien registration
Where do I file, and how do I pay?
File with the district tax office having jurisdiction over your place for tax payment — in principle a resident's domicile, or place of residence if there is no domicile (Income Tax Act art. 6). A return sent to the wrong office is forwarded to the competent one. You do not need to visit in person: you can mail the forms, or file electronically at Hometax (www.hometax.go.kr).
| Filing method | How to access |
|---|---|
| Hometax e-filing | www.hometax.go.kr → Log in → File/Pay → Tax return filing → Global income tax |
| Mobile e-filing | Install the Hometax app → Log in → File/Pay → Global income tax |
| Tax agent | Seek help from a licensed tax accountant for bookkeeping, etc. |
| In person / by post | Download the form from www.nts.go.kr, complete it, and mail it to the jurisdictional office or hand it in |
Hometax is Korean-only
How to pay
| Method | How to access |
|---|---|
| Hometax | Log in → Payment / Notice / Refund → Search and pay → Pay → choose account transfer, credit card or simple payment (07:00–23:30) |
| CardroTax / Internet Giro | www.cardrotax.kr or www.giro.or.kr → Log in → National tax → Search-and-pay or voluntary payment (00:30–23:30) |
| In person | Take the payment form to a bank or post office |
Paying in installments
Penalties, refunds and overseas income
If you file late
Filing or paying late triggers penalty tax for non-compliant filing and for late payment. See Part 5 for the rates.
Receiving a refund
When a refund is due, the district tax office remits it to your Korean bank or post-office account by the end of June, so you must enter your account number in the refund-account field of the return. Where the refund is 50 million won or more, also submit the account-opening/change declaration (Form 22 of the Enforcement Rules of the Framework Act on National Taxes) with a copy of your bankbook. If a transfer is not possible, the refund can be collected in cash at a post office with the refund notice and your ID (an agent additionally needs both IDs and a sealed letter of attorney).
Accounts that cannot receive refunds
Do I report income earned overseas?
Residents are taxed on worldwide income; non-residents only on Korean-source income (Income Tax Act art. 3). A resident converts foreign-source income to won at the basic or arbitrage exchange rate on the date the income arose (Enforcement Rules art. 16). Short-stay exception: for income first arising on or after Jan. 1, 2009, a foreign resident whose total domicile/residence in Korea is 5 years or less within the preceding 10 years is taxed on foreign-source income only to the extent it is paid in or remitted to Korea. Foreign tax paid on foreign-source income can be relieved through the foreign tax credit.
Double-entry vs. simplified bookkeeping
Business operators must keep books under the double-entry system so that every transaction can be objectively identified (Income Tax Act art. 160). Smaller businesses may instead keep a simplified book recording sales, expenses and changes in tangible/intangible business assets (NTS Notice 2024-19).
Who may use simplified bookkeeping (Enforcement Decree art. 208)
New businesses in 2025, and continuing businesses whose 2024 revenue is below the threshold below. Medical, legal and other listed professional occupations are always excluded.
| Industry group | Threshold (2024 revenue) |
|---|---|
| Farming, forestry & fishing; mining; wholesale/retail (excl. commodity brokerage); real-estate brokerage; anything not in groups 2 or 3 | under 300 million won |
| Manufacturing; lodging & food service; utilities; water/sewage/waste/recycling; construction (excl. non-residential buildings); residential real-estate development & supply; transport & storage; information & communication; finance & insurance; commodity brokerage | under 150 million won |
| Real-estate lease; real-estate services (excl. sales); professional/scientific/technical services; business-support & lease services; education; health & social welfare; arts/sports/leisure; associations; repair & personal services; household employment | under 75 million won |
Bookkeeping incentive and penalty
- A simplified-bookkeeping business that voluntarily keeps double-entry books gets a 20% tax credit for bookkeeping (up to 1 million won/year) — lost if 20%+ of income is omitted, or books are not kept for 5 years.
- A business that keeps no books faces a 20% non-bookkeeping penalty tax (about 30%+ more tax than if books were kept), except new businesses and those with prior-year revenue under 48 million won.
Standard & simplified expense rates (filing by estimation)
Every business should file from its own books. Because a self-employed taxpayer who keeps no books cannot compute exact income, income is estimated by applying a government expense rate to revenue.
Standard expense rate
Income = Gross revenue − primary expenses (with documents) − (Gross revenue × standard expense rate). Primary expenses are purchases, rent and wages, verified by tax invoice, invoice, credit-card slip or cash receipt (a “statement of primary expenses” is needed for simplified invoices/receipts; wages need a withholding receipt or payment statement). Double-entry taxpayers apply 50% of the standard expense rate. To cap sudden increases, the estimated income may instead be the lesser of the standard-rate figure and {Gross revenue − (Gross revenue × simplified rate)} × multiplier (2.8× for simplified-bookkeeping, 3.4× for double-entry).
Simplified expense rate
Income = the lesser of [Gross revenue − (Gross revenue × simplified rate)] and the standard-rate income.
Who falls under which rate (Enforcement Decree art. 143(4))
| Industry group | Simplified rate if 2024 revenue is below / new-business 2025 revenue below | Otherwise: standard rate |
|---|---|---|
| Group 1 (see above) | 60 million won / 300 million won | at or above |
| Group 2 | 36 million won / 150 million won | at or above |
| Group 3 | 24 million won / 75 million won | at or above |
Always on the standard rate
- Professional occupations (lawyer, tax accountant, accountant, customs broker, doctor, pharmacist, veterinarian, etc.)
- Businesses required to register as a cash-receipt store that have not done so
- Habitual refusers of credit-card/cash-receipt issuance (3+ times/year totalling 1M won+, or 5+ times/year)
Disabled taxpayers and personal-service earners
- Disabled taxpayer (with a certificate, running the business personally): simplified rate = simplified rate + (100% − simplified rate) × 20% (cut to two decimals). No such exception for the standard rate.
- Personal-service earners (business code 94****): a basic rate applies to revenue up to 40 million won and an excess rate to the amount above. Example — a salesperson (940908) with 45,000,000 won revenue: 45,000,000 − [(40,000,000 × 75.0%) + (5,000,000 × 65.0%)] = 11,750,000 won.
Summary of 2025 tax-law changes
- Child tax credit increased (art. 59-2): 1st child 150,000 → 250,000 won; 2nd 200,000 → 300,000; 3rd and beyond 300,000 → 400,000 won each.
- Stronger withholding on foreign professional athletes (art. 129): 20% withholding now applies regardless of contract length (previously only for contracts of 3 years or less).
- Income-tax reduction extended to highly-skilled foreign professionals (K-tech Pass holders) — eligibility for the 50% reduction (10 years, sunset Dec. 31, 2026) now also covers outstanding foreign talent under the Special Act on Fostering and Securing Talents for Strategic Industries.
- New marriage tax credit (Restriction of Special Taxation Act art. 92): 500,000 won, once per lifetime, for a resident who registers a marriage in 2024–2026.
- Void-marriage rules for the marriage credit: if the marriage is annulled and an amended/late return is filed within 3 months, non-filing/under-reporting and late-payment penalties are waived, but interest (500,000 × days × 0.022%/day) is added.
- Housing-savings deduction widened: the spouse of a non-homeowner household head with earned income — where the spouse is a foreign employee resident in Korea — may also take the 40% deduction (annual limit 3 million won; total salary 70 million won or less).