Business Income Tax Calculator
Calculate a sole proprietor's comprehensive income tax (business income) based on revenue and necessary expenses.
Revenue & Expenses
Total actual expenses per books
National pension, Nano Umbrella mutual aid, etc.
Standard tax credit ($70), child, pension account, etc.
Total Tax Payable (Income + Local Tax)
₩4,889,500
* Reference calculation without regard to standard/simplified expense rate eligibility, thorough reporting, or exemptions. Reconciled with prepaid tax (interim payments/withholding).
Related life info & benefits
The business income tax calculator computes comprehensive income tax based on a sole proprietor's business income — total revenue minus necessary expenses. It applies to registered sole proprietors, whose filing method differs from freelancers subject to 3.3% withholding.
How necessary expenses are recognized
If you keep books, your actual expenses are recognized as-is; without books, you file using an estimated method based on an industry expense ratio (simplified or standard rate). The higher your revenue, the more likely the standard expense rate applies, which recognizes a lower proportion of expenses.
The comprehensive income tax rate applies directly
Business income is combined with other comprehensive income (wage, other income, etc.) and taxed at the 6–45% progressive rate. Unlike wage-only earners, you must file and pay directly every May.
Frequently Asked Questions
How do I file without keeping books?
You can use the estimated filing method, applying the industry's simplified or standard expense ratio to your revenue to estimate necessary expenses.
What's the difference between the simplified and standard expense ratio?
If revenue is under a certain threshold, the simplified ratio (which recognizes more expenses) applies; above that, the standard ratio applies, requiring separate documentation for major expenses like labor and rent.
Do sole proprietors pay the four social insurances too?
If you hire employees, you must enroll them as workplace-based subscribers; the owner separately enrolls in health insurance and national pension as a regional (self-employed) subscriber.
Are VAT and comprehensive income tax filed separately?
Yes — VAT is filed 1–2 times a year based on revenue, while comprehensive income tax is filed every May based on net income.
What happens if my business runs a loss?
If you keep books, the loss can be carried forward up to 15 years and offset against future income.
* Based on 2026 figures. Actual tax depends on whether you keep books and which expense-ratio method applies.
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