2026 Korea Comprehensive Income Tax Calculator | Tax Brackets, Filing Guide & Refunds

Introduction: May Is When the Year-End Reckoning Begins

For self-employed business owners and freelancers in Korea, May is the decisive month when an entire year of economic activity is settled. Salaried employees finish their year-end tax adjustment in January and February, but anyone who earns business income, miscellaneous income, or rental income must personally file Comprehensive Income Tax (jonghap-sodeukse, 종합소득세) between May 1 and May 31. Taxpayers subject to the Sincere Filing Confirmation system get an additional month, until June 30.

The challenge is that the Comprehensive Income Tax is not simply "revenue × tax rate." To arrive at the final amount, you must subtract necessary expenses from total income, apply various income and tax credits, and determine which of the eight progressive tax brackets applies. Freelancers, on top of that, have already had 3.3% withheld from their business income (3% income tax + 0.3% local income tax), so in many cases the end result is not additional tax due but a refund to be claimed.

This article lays out the structure of the Comprehensive Income Tax in one place, based on the 2025 tax year (filed in May 2026). Start by estimating your tax with the interactive calculator at the top of the page, then follow the guide below through filing requirements, tax brackets, deductions, the Hometax (Korea's National Tax Service online portal) filing process, and what to do if you miss the deadline. This single page should be all you need to prepare for the May filing.

1. Who Must File for 2026 and When

1.1 Who has a filing obligation — if any one of these five applies, you must file

The Comprehensive Income Tax combines six income categories for taxation: interest, dividend, business, employment, pension, and miscellaneous income. Not every citizen has to file, however. You are required to file if any of the following five conditions apply.

• 1. Self-employed / individual business owners: Any sole proprietor with business income — retail, restaurants, services, e-commerce, and so on — should file even when the business posts a loss, so that the loss can be carried forward to offset future years.
• 2. Freelancers and personal service providers: Writers, instructors, designers, developers, delivery riders, and anyone else whose business income has had 3.3% withheld at source must file.
• 3. Miscellaneous income above 3 million KRW per year: If miscellaneous income such as lecture fees, writing fees, or prize money (after deducting necessary expenses) exceeds 3 million KRW, it must be included in comprehensive taxation. Amounts of 3 million KRW or less may be taxed separately.
• 4. Residential rental income above 20 million KRW per year: Rental revenue over 20 million KRW must be filed under comprehensive taxation. If it is 20 million KRW or less, you can choose between comprehensive taxation and separate taxation (14%), whichever is more favorable.
• 5. Financial income above 20 million KRW per year, or employment income from two or more employers: You must file directly when the total of interest and dividend income exceeds 20 million KRW, or when you have not consolidated wages earned from multiple employers.

1.2 Filing period — regular vs. Sincere Filing Confirmation

The filing and payment window differs by taxpayer type.

• Regular filing: May 1 through May 31, 2026 (extended to the next business day if the deadline falls on a weekend or holiday).
• Sincere Filing Confirmation taxpayers: May 1 through June 30, 2026. Thresholds vary by industry: 1.5 billion KRW for wholesale/retail, 750 million KRW for manufacturing/construction, 500 million KRW for services.

Sincere Filing Confirmation taxpayers must attach a certified confirmation from a licensed tax agent, and 60% of the verification cost (up to 1.2 million KRW) is refundable as a tax credit.

1.3 Penalties if you miss the deadline

Missing midnight on May 31 brings a cascade of penalties.

• Non-filing penalty: 20% of tax due (40% for fraudulent non-filing; 60% for fraudulent international transactions).
• Late-payment penalty: unpaid tax × days late × 0.022% (approximately 8.03% per year).
• No-bookkeeping penalty for double-entry bookkeeping filers: an additional 20% of the calculated tax.

For example, if you owed 3 million KRW and failed to file at all, the non-filing penalty alone is 600,000 KRW, plus daily late-payment interest; within a few months, the bill can easily swell to over 4 million KRW. Filing within May is by far the cheapest path.

2. How the Taxable Base Is Determined

2.1 The core formula — start from total income, subtract expenses and deductions

Every Comprehensive Income Tax calculation begins with the taxable base.

Taxable Base = Total Income − Necessary Expenses − Income Deduction
Calculated Tax = Taxable Base × Rate − Progressive Deduction
Total Tax Due = Calculated Tax + Local Income Tax (10%) − Tax Credits − Tax Already Withheld

Total income is "total revenue," while necessary expenses are "money spent for business purposes" — rent, payroll, materials, advertising, telecommunications, vehicle fuel, and so on. All of these count, but only if you have valid documentation (tax invoices, card slips, cash receipts).

2.2 Simple vs. standard expense rate — what if you do not keep books?

Taxpayers who do not keep books file via an estimated return, applying industry-standard expense rates.

• Simple expense rate: for small businesses with modest revenue (e.g. new or micro freelancers). For instance, if the simple expense rate for personal-service freelancers is 64.1%, a 30 million KRW income is automatically recognized as having 19.23 million KRW in expenses.
• Standard expense rate: applied when revenue is too large for the simple-rate regime. Major expenses (purchases, rent, payroll) must be backed by documentation; only the remaining portion is recognized at the standard rate. In practice this rate is 10-20% of the simple rate — much less generous.

Which rate applies depends on both your industry and your revenue, so be sure to check the expense rate for your business-type code in the Hometax expense-rate lookup menu.

2.3 Income deductions — basic and additional

Once your income figure (revenue minus expenses) is set, you apply income deductions to finalize the taxable base. The major deductions are listed below.

• Basic personal deduction: 1.5 million KRW, unconditionally applied to every filer.
• Spouse and dependents: 1.5 million KRW each, for each family member whose annual income is 1 million KRW or less (or, for employment-only income, total salary of 5 million KRW or less).
• Additional deductions: senior (age 70+) 1 million KRW, disabled person 2 million KRW, qualifying woman 500,000 KRW, single parent 1 million KRW.
• National Pension and National Health Insurance premiums: fully deductible.
• Noranumbrella (Yellow Umbrella) Mutual Aid: mutual-aid contributions for small-business owners, with an annual limit of 2 to 5 million KRW depending on income bracket.

3. 2025 Tax Year Bracket Table — Eight Progressive Brackets

Once the taxable base is set, it is taxed according to the eight progressive brackets below. Note that the same rate is not applied to the full amount — different rates apply to different portions of the taxable base. The progressive deduction column makes the calculation simple.

Taxable Base Range	Rate	Progressive Deduction
Up to 14,000,000 KRW	6%	0 KRW
14,000,000 to 50,000,000 KRW	15%	1,260,000 KRW
50,000,000 to 88,000,000 KRW	24%	5,760,000 KRW
88,000,000 to 150,000,000 KRW	35%	15,440,000 KRW
150,000,000 to 300,000,000 KRW	38%	19,940,000 KRW
300,000,000 to 500,000,000 KRW	40%	25,940,000 KRW
500,000,000 to 1,000,000,000 KRW	42%	35,940,000 KRW
Over 1,000,000,000 KRW	45%	65,940,000 KRW

3.1 Concrete examples

A few worked examples using the table above.

• Taxable base 30,000,000 KRW (15% bracket): 30,000,000 × 15% − 1,260,000 = 3,240,000 KRW (3,564,000 KRW including local tax).
• Taxable base 60,000,000 KRW (24% bracket): 60,000,000 × 24% − 5,760,000 = 8,640,000 KRW (9,504,000 KRW including local tax).
• Taxable base 100,000,000 KRW (35% bracket): 100,000,000 × 35% − 15,440,000 = 19,560,000 KRW (21,516,000 KRW including local tax).
• Taxable base 200,000,000 KRW (38% bracket): 200,000,000 × 38% − 19,940,000 = 56,060,000 KRW (61,666,000 KRW including local tax).

Thanks to the progressive deduction, you do not need to break the base into pieces ("6% up to 14M, 15% up to 50M…"). A single line of multiplication produces the same result. The calculator at the top of this page uses exactly this logic.

4. Five Must-Check Deduction Categories

Deductions are a "pay less if you know about them" system. Missing one means paying more than you needed to, so go through each of the items below.

4.1 Personal deductions — self, spouse, and dependents

You yourself always receive a 1.5 million KRW deduction. Your spouse and dependents qualify for 1.5 million KRW each if their annual income is 1 million KRW or less. Age requirements for dependents are: direct ascendants aged 60 or older; direct descendants aged 20 or younger; siblings aged 20 or younger or 60 or older. There is no age requirement for a person with a disability.

4.2 Additional deductions — an extra amount on top of the basic

In addition to the basic deductions, the following can be applied.

• Senior citizen (age 70 or older): 1 million KRW per person.
• Person with a disability: 2 million KRW per person.
• Qualifying woman (married woman or female head of household with dependents, income of 30 million KRW or less): 500,000 KRW.
• Single parent (unmarried with dependent children): 1 million KRW — takes precedence over the qualifying-woman deduction if both apply.

4.3 Special income deductions and tax credits — items you must claim yourself

• Medical expense credit: 15% of expenses exceeding 3% of total salary (30% for infertility treatment, 20% for premature infants and serious illnesses). No ceiling for the taxpayer, people 65 or older, and people with disabilities; 7 million KRW per year ceiling for other dependents.
• Education expense credit: 15% of expenses up to the full amount for self, 9 million KRW per year for a child in university, and 3 million KRW per year for kindergarten through high school.
• Donation credit: 15% for donations up to 10 million KRW, 30% for the portion above. For political donations up to 100,000 KRW, the entire amount is refunded as a tax credit.
• Monthly rent credit: 17% (for total salary of 55 million KRW or less) or 15% of annual rent up to 10 million KRW, available to heads of non-homeowner households with total salary of 80 million KRW or less.

4.4 Tax credits — pension accounts, children, bookkeeping

• Child tax credit: 250,000 KRW for one child aged 8 or older, 550,000 KRW for two, and 400,000 KRW for each additional child beyond two. (The 2024-tax-year increase from 150,000 to 250,000 KRW for the first child remains in effect.)
• Pension accounts (pension savings + IRP): 12% of contributions up to 9 million KRW per year (6 million KRW if pension savings only), or 15% if total salary is 55 million KRW or less. Filling the 9 million KRW limit can yield up to 1.35 million KRW back as a credit.
• Bookkeeping credit: For simple-bookkeeping taxpayers who choose to keep double-entry books, 20% of the calculated tax, capped at 1 million KRW per year.

4.5 Standard tax credit — if everything else is too much trouble

If you claim no special deductions at all (medical, education, donations, etc.), a standard tax credit of 130,000 KRW is applied automatically (70,000 KRW for salaried employees). If you have no documentation and your deductions would come in below 130,000 KRW anyway, the standard credit is the better choice.

5. A Practical Hometax Filing Guide

5.1 "Modu-Chaeum" pre-filled service — let the NTS do the math for you

Since 2020, the National Tax Service (NTS, 국세청) has offered a Modu-Chaeum pre-filled service. For small businesses and freelancers eligible for the simple expense rate, the NTS mails out a pre-calculated return, and you only need to confirm it to complete the filing. Tax due or refund amounts are computed automatically, and the whole process takes just a few taps in the Sontax (mobile Hometax) app. Notifications go out from late April, so keep an eye on your physical mail and the NTS "Alim-Talk" notifications on KakaoTalk.

5.2 The eight-step electronic filing process — if you file yourself

1. Log in to Hometax (hometax.go.kr) using a joint certificate, financial certificate, or simple authentication (KakaoTalk, PASS, etc.).
2. Go to "Report/Payment" → "Tax Report" → "Comprehensive Income Tax."
3. Choose your filing type (simple expense rate, standard expense rate, simple bookkeeping, or double-entry bookkeeping).
4. Review your basic information — business registration, dependents, and last year's filing history are imported automatically.
5. Enter your revenue and necessary expenses. Much of the sales and purchase data is pulled in from Hometax automatically.
6. Enter your income deductions and tax credits. Data from the Year-End Tax Settlement Simplified Service can be reused as is.
7. Check the tax calculation. The calculated tax, local income tax, and the amount to be paid (or refunded) are computed automatically.
8. Submit the electronic return, then register your payment or refund account.

5.3 Payment options — pay in full or spread it out

• Direct debit / one-click payment via Hometax: the fastest method, with no fees.
• Credit or debit card: via Cardrotax (cardrotax.kr) or Hometax. Card fees are paid by the taxpayer (0.8% credit, 0.5% debit).
• Virtual account: after filing, transfer to the dedicated virtual account you receive.
• Installment: if tax due is above 10 million KRW, you may split payment over two months. If above 20 million KRW, you can pay 50% now and 50% within two months.

6. When You Miss It — Late Filing, Amended Filing, and Refund Claims

6.1 Late filing — if you missed the filing itself

Even if you miss May 31, filing a late return as soon as possible will reduce the penalties.

• Within 1 month: 50% reduction of the non-filing penalty → effective 10%.
• Within 3 months: 30% reduction → 14%.
• Within 6 months: 20% reduction → 16%.

Do not leave it; finishing a late filing within at least a month is the wisest approach.

6.2 Amended filing — if you paid too little

If your original return understated your income or overstated your expenses and you therefore underpaid, filing an amended return before receiving a tax-audit notice reduces the underreporting penalty by up to 90%. Reductions scale with timing: 90% within 1 month, 75% within 3 months, 50% within 6 months, 30% within a year, 20% within 18 months, and 10% within 2 years.

6.3 Refund claim (gyeongjeong-cheonggu, 경정청구) — recover overpaid tax within five years

Conversely, if you overpaid, you can recover the difference through a refund claim. The deadline is five years from the original statutory filing deadline, so returns filed for tax year 2020 (filed in May 2021) can still be amended via a refund claim up to the end of May 2026. Commonly missed items include medical, education, rental, and donation deductions, as well as additional dependents. It is worth reviewing the past five years of year-end tax settlements and Comprehensive Income Tax returns; in many cases the refund exceeds the tax-advisor fee.

Conclusion: Do Not Wait Until May — Start Preparing in April

The Comprehensive Income Tax is not really a "one-month-in-May" affair. It is, in effect, a report card showing how thoroughly you documented your finances over the past year. Arriving in May without books often means filing unfavorably under simple or standard expense rates, and missing one deduction after another. Run through the ten-item checklist below once in April and once more just before filing in May.

1. Are all your annual sales and purchase tax invoices, credit card slips, and cash receipts registered on Hometax?
2. Have you organized expense documentation for payroll, rent, vehicle maintenance, telecommunications, and so on by month?
3. Have you reconfirmed the income threshold (1 million KRW per year or less) for yourself, your spouse, and your dependents?
4. Have you downloaded medical, education, donation, and rental data from the Year-End Tax Settlement Simplified Service?
5. Have you maxed out the 9 million KRW pension savings / IRP limit to claim the 1.35 million KRW tax credit?
6. If you have children aged 8 or older, did you apply the child tax credit (for example, 550,000 KRW for two children)?
7. As a Yellow Umbrella member, have you contributed up to the income-bracket limit?
8. If you are subject to Sincere Filing Confirmation, is your tax agent's confirmation document ready?
9. If your tax due exceeds 10 million KRW, have you planned for the installment application?
10. Have you reviewed the past five years of Comprehensive Income Tax returns for potential refund-claim opportunities?

Finally, remember that the calculator at the top of this page produces only an estimate. For the actual filing, always make your final confirmation on the NTS Comprehensive Income Tax guide page and the official Hometax calculator. If complex deductions are involved, calling the NTS Consultation Center at 126 for free advice is a good idea. Do not wait until May — start preparing in April.