Filing 종합소득세 in Korea: Freelancer's Guide [2026]

This article provides general information about Korean tax filing procedures. It is NOT tax advice. Tax situations are individual. Consult a qualified 세무사 (certified tax agent) before making decisions.

The 3.3% Is Not Your Tax Bill

Every freelancer in Korea learns the number fast. You invoice ₩1,000,000. You receive ₩967,000. The client kept ₩33,000. That's the 3.3%.

Here's what that number actually is: 3% income tax plus 0.3% local income tax. Your client withholds it and sends it to the 국세청 (National Tax Service) on your behalf. Think of it as a deposit. A forced savings account toward your real tax bill, which you won't know until May.

The problem? 3.3% has almost nothing to do with what you actually owe.

Korea's income tax brackets run from 6% to 45%. If you earned ₩50M in freelance income last year, your effective rate after deductions might land somewhere around 10-15%. The 3.3% you already paid? That goes toward that bill. If it's not enough (it usually isn't for higher earners), you pay the difference. If you overpaid, you get a refund.

Most freelancers earning under ₩20M or so will overpay through withholding. Most earning above ₩40M will underpay. The middle is a coin flip depending on your deductions.

The point: 3.3% is not a tax rate. It's a prepayment mechanism. Your actual tax rate depends on your total income, your deductions, and which bracket you fall into. That gets settled in May, when you file 종합소득세 (jong-hap-so-deuk-se), literally "comprehensive income tax."

Do You Need to File?

Short answer: probably yes. But let's be specific.

You must file 종합소득세 if:

• You received freelance income in Korea (the 3.3% withholding kind)
• You had income from two or more sources (freelance plus employment, for example)
• You earned rental income, interest/dividend income above ₩20M, or other non-wage income
• You're a Korean tax resident (183+ days in a calendar year, or 183 consecutive days spanning two years)

You might not need to file if:

• You had only one employer and no side income (your company did year-end settlement for you)
• Your total income was below the basic deduction threshold (roughly ₩1.5M after standard deductions, which is... not a lot)

The residency question matters. If you've been in Korea for 183 days or more, Korea considers you a tax resident. That means worldwide income is potentially taxable (with some exceptions for foreign-source income in your first 5 years). If you've been here less than 183 days, only Korean-source income gets taxed.

The day-counting rules are more complicated than they look. Korea uses both calendar-year counting and consecutive-day counting, and whichever triggers first wins. For the full breakdown of how Korea, Japan, and Taiwan each count differently: 183-Day Tax Trap: Korea, Japan & Taiwan.

Visa type doesn't determine your tax obligation. Whether you're on an F-1-D workation visa, a D-8 startup visa, or any other status, the tax rules follow residency days, not visa category. An F-1-D holder here for 200 days files the same as a D-8 holder here for 200 days.

One exception worth noting: if you're on a short-term visa and earned only Korean-source freelance income, you still need to file if the 3.3% withholding doesn't match your actual liability. The NTS doesn't care about your visa. They care about your income.

What You Owe: Tax Brackets and the Flat Rate

Korea uses a progressive tax system. The more you earn, the higher the rate on each additional slice of income. Here are the 2026 brackets for 종합소득세:

Add 10% local income tax on top (지방소득세). So a 15% bracket actually means 16.5% total. A 24% bracket means 26.4%. And so on.

The 19% flat rate option. Foreign workers (employees, not freelancers) can elect a flat 19% rate (20.9% with local tax) under 조세특례제한법 Article 18-2. This is available for 20 consecutive years from your first work date. But there's a catch: it applies to employment income only. Freelance income doesn't qualify. If you're a salaried worker with a side freelance gig, the flat rate covers only the salary portion. The freelance income gets taxed at progressive rates.

For most freelancers reading this, the progressive brackets are your reality. The flat rate is someone else's benefit.

For the full breakdown of the flat rate, treaty provisions, and country-specific rules: Korea Double Tax Treaty Guide.

Expense Deductions Freelancers Can Claim

This is where freelancing in Korea gets interesting. You have two paths for deducting business expenses, and which one applies depends on your revenue.

Path 1: 단순경비율 (dansun-gyeongbi-yul, "simple expense ratio")

If your gross revenue is below a certain threshold (varies by industry, but roughly ₩24M-75M depending on your business category), you can use the simple expense ratio. The NTS assigns a percentage based on your industry code. For most freelance work (writing, design, consulting, software), the rate falls between 60-80%.

That means the NTS assumes 60-80% of your revenue went to expenses. You get taxed only on the remaining 20-40%. No receipts needed. No record-keeping headaches. Just a formula.

For a freelancer earning ₩30M with a 64.1% simple expense ratio, taxable income drops to roughly ₩10.8M. At the 6% bracket, that's a very manageable tax bill. Probably less than the 3.3% already withheld. Refund territory.

Path 2: 기준경비율 (gijun-gyeongbi-yul, "standard expense ratio")

If your revenue exceeds the simple ratio threshold, you switch to the standard expense ratio. This one is less generous. The NTS still applies a base ratio (usually 10-30% depending on industry), but you must document and prove major expenses yourself: rent, salaries, material costs, depreciation.

This is where keeping receipts matters. 현금영수증 (hyeon-geum-yeong-su-jeung, cash receipts) and 세금계산서 (se-geum-gye-san-seo, tax invoices) become your best friends.

Common deductible categories for freelancers:

• Office rent or coworking space fees
• Equipment (laptop, monitor, peripherals)
• Software subscriptions used for work
• Transportation for client meetings
• Communication costs (phone, internet, proportional)
• Professional development and training
• National Pension and health insurance premiums (the mandatory kind)

Filing on Hometax: Step by Step

홈택스 (Hometax) is the NTS online filing system. The filing period for 2025 income is May 1-31, 2026. Miss it and penalties start accumulating.

Before you start, gather these:

• Your ARC number (외국인등록번호) or Korean ID number
• 홈택스 login credentials (certificate-based or simple auth)
• Income records: 원천징수영수증 (withholding receipts) from all clients
• Expense documentation (if using standard expense ratio)
• Bank account for refund deposits

The filing process:

Step 1: Log in to 홈택스. There's a partial English interface available by clicking the globe icon in the top-right corner. Fair warning: the English version covers maybe 60% of what you need. Key tax filing screens often revert to Korean. Google Translate on your phone, pointing at your monitor, will become a tool you use without shame.

Step 2: Find the 종합소득세 filing menu. In Korean, it's under 신고/납부 (filing/payment) → 종합소득세. In the English interface, look for "General Income Tax Return." The system pre-populates some of your data from employer and client withholding reports.

Step 3: Verify your income. Hometax pulls your 3.3% withholding records automatically. Check that every client who withheld tax appears in the pre-filled data. If a client reported late or incorrectly, you'll need to input that income manually. This happens more than you'd expect.

Step 4: Select your expense deduction method. The system will show whether you fall under 단순경비율 or 기준경비율 based on your revenue and business code. Select the appropriate one. If using standard ratio, you'll need to enter documented expenses here.

Step 5: Apply deductions and credits. Personal deductions (인적공제), pension contributions, health insurance, and other credits get applied here. The system walks you through each category. Some items are pre-filled from your employer's year-end data. For freelance-only filers, you'll enter these manually.

Step 6: Calculate and review. Hometax computes your total tax, subtracts the 3.3% already paid, and shows either a balance due or a refund amount. Review everything before submitting.

Step 7: Pay or wait. If you owe, pay by May 31 through Hometax's integrated payment system (bank transfer or card). If you're owed a refund, it hits your registered Korean bank account in 2-4 weeks after filing.

삼쩜삼 and Other Tax Apps: Can Foreigners Use Them?

삼쩜삼 (sam-jjeom-sam, literally "3.3," stylized as "3o3") is Korea's most popular tax filing and refund app. Over 20 million Koreans have used it. The pitch is simple: connect your data, and the app calculates whether you overpaid taxes. If you did, they file for a refund. Their fee is a percentage of the refund amount.

Does it work for foreigners? Technically, yes. You need an ARC number and a Korean phone number to sign up. The app pulls your withholding data from the NTS the same way it does for Korean users.

The limitations are real, though.

The interface is Korean-only. No English option. If you can't read Korean tax terminology (or aren't comfortable with translation apps handling your financial data), this becomes a stressful experience rather than a convenient one.

삼쩜삼 works best for simple cases. One or two income sources, standard deductions, no unusual tax situations. If you have foreign-source income, treaty considerations, or income from multiple countries, the app won't handle that. It's built for the common Korean freelancer case.

The app also doesn't handle 기준경비율 (standard expense ratio) filers who need to document specific expenses. If you're above the simple ratio threshold and need to itemize, 삼쩜삼 can't help you there.

Other apps worth knowing: SSEM (쎔) is another popular option with similar functionality. Taxly targets a slightly more sophisticated user. None of them currently offer English interfaces.

The honest take: if your situation is straightforward (freelance income only, under the simple ratio threshold, no foreign income complications), 삼쩜삼 can save you time and catch refunds you'd miss doing it yourself. Their fee is worth it for the convenience. But if your tax situation involves anything beyond a basic Korean freelance setup, you need a human. Specifically, a 세무사.

When to Hire a 세무사 (and What It Costs)

세무사 (se-mu-sa) means "certified tax agent." It's a licensed profession in Korea, regulated by the 세무사법 (Tax Agent Act). They're not accountants in the Western sense. They're specialists in Korean tax filing, and they carry legal authority to represent you before the NTS.

You probably don't need one if:

• Your only income is Korean freelance income under ₩24M
• Your income falls under the 단순경비율 (simple expense ratio) threshold
• You have no foreign income or treaty considerations
• You're comfortable with Hometax (or 삼쩜삼 works for your case)

You probably do need one if:

• You earn from both Korean and foreign sources
• Your income exceeds the simple expense ratio threshold
• You need to claim specific business deductions with documentation
• You're trying to determine whether tax treaty provisions apply
• You're leaving Korea and need departure tax clearance
• You received income through a Korean entity AND as an independent contractor in the same year

What it costs: basic freelancer 종합소득세 filing runs ₩100,000-300,000 depending on complexity. For simple cases, ₩100,000-150,000 is common. If you have multiple income sources, foreign income, or need treaty analysis, expect ₩200,000-300,000 or more.

Finding an English-speaking 세무사: they exist, but they're concentrated in Seoul (Gangnam, Itaewon, Yongsan areas). The Seoul Global Center offers free tax consultations during filing season, which is genuinely useful for sorting out whether you need professional help. Some international law firms and accounting firms (Samil PwC, Deloitte Anjin, KPMG Samjong) have English-speaking tax teams, but their fees are significantly higher, typically ₩500,000+.

For most freelancers earning ₩30-80M, hiring a 세무사 at ₩150,000-200,000 often pays for itself through deductions and credits you wouldn't find on your own.

Penalties and Common Mistakes

Missing the May 31 deadline hurts. Here's how:

Late filing penalty: 20% of the unpaid tax amount. If you owed ₩1,000,000 and filed in July, that's an extra ₩200,000. File before the deadline but pay late? The penalty drops to roughly 0.022% per day on the unpaid amount (about 8% annualized). Still not fun.

Underreporting penalty: if the NTS determines you reported less income than you earned, the penalty is 10% of the underreported tax for a simple omission. If they decide it was intentional, that jumps to 40%. Don't play games with unreported income. Korean clients report their 3.3% withholding to the NTS. The data is already there.

Common foreigner mistakes:

Forgetting foreign income. If you're a Korean tax resident (183+ days) and past your first 5 years, worldwide income is taxable. That US client paying into your American bank account? Korea wants to know about it.

Not filing because "I'm leaving soon." You still need to file for the income year. If you're departing Korea before May, you can file early. The NTS allows pre-deadline filing. If you're leaving Korea permanently, there's a departure tax clearance process. More on that: Leaving Korea Money Checklist.

Using the wrong expense ratio. If you fall under 단순경비율 but select 기준경비율 (or vice versa), your tax calculation will be wrong. The Hometax system usually catches this, but manual overrides are possible and sometimes people make them by accident.

Missing the NPS/health insurance deductions. Your mandatory National Pension and National Health Insurance contributions are deductible. These amounts aren't trivial. A freelancer paying ₩200,000/month in NPS and ₩150,000/month in health insurance has ₩4.2M in deductions right there. Don't forget them.

FAQ

Q: What is the 3.3% withholding tax in Korea?

A: It's 3% income tax plus 0.3% local income tax, withheld at source by the entity paying you. It's a prepayment toward your annual 종합소득세, not your final tax rate. You settle the actual amount when you file in May.

Q: Can foreigners file 종합소득세 on Hometax?

A: Yes. You need an ARC number and Hometax login credentials (공동인증서 from a Korean bank, or simplified auth through Kakao/PASS). The partial English interface helps but doesn't cover all filing screens.

Q: What happens if I don't file by May 31?

A: Late filing penalty of 20% on the unpaid tax amount, plus daily interest. If you're owed a refund, late filing doesn't add a penalty, but you delay getting your money back. The refund right expires after 5 years.

This article is for informational purposes only and does not constitute tax, legal, or financial advice. Korean tax law is complex and changes frequently. Individual circumstances vary. Always consult a licensed 세무사 (certified tax agent) for advice specific to your situation.

Ready to sort out more than just taxes? Start with our Korea Digital Nomad Guide for the full picture of living and working here.