Chapter Key Takeaways
| Bookkeeping Types | Double-Entry Bookkeeping (복식부기) vs Simplified Ledger (간편장부) |
|---|---|
| Estimation Methods | Simplified Expense Rate (단순경비율) vs Standard Expense Rate (기준경비율) |
| Freelancer Threshold | Simplified rate applies if prior year revenue < 24M KRW (or current year < 75M KRW for new businesses) |
| Double-Entry Threshold | Service / Freelance: Prior year revenue ≥ 75M KRW (requires certified accountant filing) |
| Non-Bookkeeping Penalty | 20% penalty tax (무기장가산세) if required bookkeeper files via estimated expense rate |
| Bookkeeping Tax Credit | 20% tax credit (up to 1,000,000 KRW) if a simplified bookkeeper voluntarily keeps double-entry books |
| Non-Filing Penalty | 20% general non-filing penalty / 40% intentional fraud penalty |
1. Bookkeeping Obligations: Simplified Ledger vs Double-Entry
Under Korean tax law, business income cannot simply be estimated arbitrarily. The law classifies every sole proprietor and freelancer into one of two bookkeeping categories based on their previous year's gross revenue:
| Category | Revenue Threshold (Services / 3.3% Freelancers) | Filing Requirements |
|---|---|---|
| Simplified Ledger (간편장부대상자) | Prior year revenue under 75 million KRW, or newly started businesses in current year. | Record daily revenues and expenses in a chronological ledger format with qualified tax receipts. |
| Double-Entry Bookkeeping (복식부기의무자) | Prior year revenue 75 million KRW or more. | Must prepare formal balance sheets and income statements following standard accounting principles. |
⚠️ Warning for Double-Entry Obligators:
If you are required to keep double-entry books but file using an estimated expense rate without a certified ledger, you will be penalized with a 20% Non-Bookkeeping Penalty Tax (무기장가산세) and lose all eligible tax incentives.
If you are required to keep double-entry books but file using an estimated expense rate without a certified ledger, you will be penalized with a 20% Non-Bookkeeping Penalty Tax (무기장가산세) and lose all eligible tax incentives.
2. Estimating Income: Simplified vs Standard Expense Rates
When a taxpayer does not have books or receipts, the National Tax Service allows income calculation using statutory expense ratios:
- Simplified Expense Rate (단순경비율): Applied to micro-businesses and entry-level freelancers (prior year revenue under 24 million KRW). NTS recognizes 60% to 75% of gross revenue as necessary business expenses automatically without requiring physical receipts.
- Standard Expense Rate (기준경비율): Applied when prior year revenue is 24 million KRW or higher. NTS allows only a small basic rate (typically 10%–20%), and all major expenses (rent, merchandise purchases, employee wages) must be proven by qualified tax invoices (세금계산서, 계산서, 신용카드, 현금영수증).
3. Overview of Major Tax Penalties for Foreigners
| Penalty Type (가산세) | Rate / Penalty Formula | Trigger Condition |
|---|---|---|
| General Non-Filing (일반무신고) | 20% of calculated tax liability | Failing to submit the tax return by May 31. |
| Fraudulent Non-Filing (부정무신고) | 40% of calculated tax liability | Intentionally concealing income, using fake bank accounts, or forging receipts. |
| Late Payment Interest (납부지연) | 0.022% per day (approx. 8% per year) | Failing to pay the tax due by the statutory deadline. |
| Non-Bookkeeping (무기장가산세) | 20% of calculated tax liability | Failing to maintain required double-entry books. |
Frequently Asked Questions
No. For services, if your prior year revenue is 24 million KRW or more, you are subject to the Standard Expense Rate (기준경비율), which provides very low deductions unless you have official tax receipts. Keeping books through a tax accountant will yield a far larger refund.
If a small taxpayer who is only required to keep a simplified ledger voluntarily maintains double-entry books, the tax office grants a 20% direct tax credit (up to 1,000,000 KRW) from their calculated tax.
The 4 qualified proofs (적격증빙) are: (1) Electronic Tax Invoices (전자세금계산서), (2) Electronic Invoices (전자계산서), (3) Business Credit/Debit Card slips, and (4) Cash Receipts registered under your business/registration number (지출증빙용 현금영수증).
Official NTS Foreigner Tax Guide Series
Explore all 6 chapters compiled from the 2026 National Tax Service Individual Income Tax Guide for Foreigners:
1
2026 Filing Basics
Filing Overview & Deadlines
2
Residency Classification
Tax Resident vs Non-Resident
3
Special Tax Regimes
19% Flat Tax & Exemptions
4
Rates & Deductions
Tax Brackets & Deductions
5
Compliance & Bookkeeping
Bookkeeping, Expense Rates & Penalties
6
Official Case Studies
NTS Case Studies & 30+ FAQs
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