2026 Korean Income Tax: Separate Taxation Guide for Financial & Rental Income

📌 Quick Summary (2 weeks before May filing deadline)

• Financial income up to KRW 20M: automatic 14% separate taxation, often a major saving compared with aggregate taxation
• Rental income up to KRW 20M: 14% separate taxation available (60% expenses + KRW 4M deduction)
• Above the threshold: progressive aggregate tax rates of 6~45% apply
• Filing deadline: May 31, 2026 (20% penalty for late filing) ## What Exactly Is Separate Taxation Under Korean Income Tax? Separate taxation means certain types of income are taxed on their own at a flat 14% rate instead of being added to your other income. Since that income stays out of the progressive tax brackets (6~45%), the benefit becomes larger as your main income increases. Common examples include financial income (interest and dividends), residential rental income, daily-wage income, and pension income (up to KRW 12M annually). Aggregate taxation works the other way: all income is combined, then taxed at progressive rates. The higher your salary, the more expensive each additional won of investment income can become. With separate taxation, qualifying income is capped at 14% (15.4% including local tax), which can save hundreds of thousands of won when you stay within the threshold. ## The KRW 20M Threshold for Financial Income (Interest + Dividends) If your total interest and dividend income for the year is KRW 20M or less, separate taxation applies automatically. The tax is settled through 14% withholding (15.4% including local tax), so no additional filing is required for that income. Over KRW 20M: The excess is included in your total income and taxed at progressive rates of 6~45%. Under the "comparison taxation" rule, you pay whichever is higher: the aggregate-tax calculation, or separate taxation on KRW 20M (KRW 20M × 14%) plus aggregate tax on the remaining amount. For example, a worker with KRW 80M in salary and KRW 30M in financial income could owe roughly KRW 3.5M in additional tax under aggregate taxation. If that financial income stays at or below KRW 20M, the total tax is only 14% × 20M = KRW 3.08M. This is exactly why ISA tax-free limits are worth managing carefully. ## KRW 20M Rental Income Separate Taxation Option If your annual residential rental income does not exceed KRW 20M, you can choose separate taxation. The formula is: Taxable base = (Revenue — Necessary expenses) — Basic deduction — Additional registered-housing deduction

Tax = Taxable base × 14% (separate taxation rate) - Necessary expenses: 50% of revenue for unregistered landlords, 60% for registered landlords

• Basic deduction: KRW 4M if other aggregate income is at or below KRW 20M (KRW 4M registered, KRW 2M unregistered) Example: Rental income of KRW 18M plus KRW 15M in other income (registered landlord)
• Necessary expenses: 1,800 × 60% = KRW 10.8M
• Net rental income: 1,800 — 1,080 = KRW 7.2M
• Subtract basic deduction KRW 4M → taxable base KRW 3.2M
• Tax: 3.2M × 14% = KRW 448,000 Under aggregate taxation, the same amount would cost about KRW 7.2M × 24% (progressive rate), or roughly KRW 1.72M. In this case, choosing separate taxation saves KRW 1.27M. ## Separate vs. Aggregate Taxation — 3 Real Cases ### Case 1: Salaried Worker + Small Dividend

Salary of KRW 60M + dividend income of KRW 15M → separate taxation 14% × 1,500 = KRW 2.1M. Under aggregate taxation, the extra burden would be about KRW 3.6M. Separate taxation saves KRW 1.5M. ### Case 2: Rental Income + Day Job Rental KRW 15M + salary KRW 50M → separate taxation (1,500 × 0.4 — 400) × 14% = KRW 280,000. Aggregate taxation would be roughly KRW 1.2M. Separate taxation saves KRW 920,000. ### Case 3: High Earner's Financial Income Salary of KRW 150M + interest and dividends of KRW 22M → because the income exceeds the threshold, it is forced into aggregate taxation. The additional tax burden is roughly KRW 4.6M. For this taxpayer, keeping financial income at or below KRW 20M should be the main strategy. ## 💡 Practical Insights (Easy-to-Miss Points) Two weeks before the May filing deadline, one of the most common mistakes is failing to choose separate taxation explicitly. Even if rental income is KRW 20M or less, the separate taxation election is not automatic — you must check it on the filing form. If you leave it out, the system defaults to aggregate taxation, and getting the refund corrected later can be inconvenient. Rental income from jointly owned property must be reported by each spouse according to their ownership share. You cannot assign all of the income to one spouse. If both spouses have high primary income, joint ownership can effectively double the separate taxation threshold (KRW 20M per person), creating meaningful savings. Penalties are another reason to file on time. Filing after May 31 can trigger a 20% non-filing penalty plus 0.022% per day late payment penalty. Even if you expect a refund, submit the return by the deadline. In some cases, penalties can wipe out the refund entirely. ## Frequently Asked Questions ### Q1. How big is the tax difference between KRW 19.99M and KRW 20.01M in financial income? A: For someone earning KRW 80M in primary salary, the difference can reach approximately KRW 3.5M. That is because, under the comparison taxation rule, the 24% progressive rate under aggregate taxation can affect the entire financial income amount, not only the excess. Managing the threshold is the key tax-saving lever. ### Q2. Can I switch the rental income separate taxation election year by year? A: Yes. You can make the election each May. If rental revenue falls in a given year and aggregate taxation is more favorable, you can switch. Registered landlords almost always benefit from separate taxation because of the additional 75% deduction. ### Q3. Do ISA account dividends count toward the separate taxation threshold? A: Dividends within the ISA tax-free quota (KRW 2M general, KRW 4M working-class type) are excluded entirely from income tax calculations. Amounts above the quota are subject to 9.9% separate taxation, which is still more favorable than the standard 14%. ### Q4. Are cryptocurrency gains subject to separate taxation? A: Cryptocurrency capital gains are subject to separate taxation at 22% (after a KRW 2.5M basic deduction). The implementation date may be postponed by government policy — check the latest NTS announcements. Prepare exchange transaction history captures in advance. ### Q5. Where do I file my income tax return? A: File through the NTS Hometax portal (hometax.go.kr) → Comprehensive Income Tax Return menu. The mobile Sontax app is also supported. Filing is open May 1~31, and refunds usually arrive from late June through July. ### Q6. Can I amend a separate taxation filing after submission? A: Before the May 31 deadline, you can amend it as many times as needed. After the deadline, corrections are handled through a "request for correction" (within 5 years) or "post-deadline filing" (50% penalty reduction). --- Related tools: Real Estate Tax Calculator, Global Exchange Rate, BMI & Calorie Calculator