DIR Daily Intelligence Report

Korea Income Tax Self-Filing Complete Guide — June 1 Deadline D-12 / Hometax 10 Minutes / 6–45% Rates / Freelancer Refund Simulation + Non-Filing Penalties

Bykey_dir

Real-Time Issue · May 20, 2026

Korea Global Income Tax Self-Filing Complete Guide — June 1 deadline D-12, Hometax Modu-Chaeum auto-fill in 10 minutes. Tax rates 6–45%, flat expense ratio, refund vs additional payment simulation for freelancers, side-job earners, and sole proprietors.

getdir.app Editorial · May 20, 2026

Korea income tax self-filing Hometax June 1 deadline freelancer sole proprietor
Korea Global Income Tax Self-Filing Complete Guide — DIR.
Korea income tax filing key info June 1 deadline Hometax tax rates
Figure 1. Key numbers — June 1 deadline / 10-min Hometax / 6–45% rates / 20% penalty

The 2025 global income tax filing deadline is June 1 (D-12). This covers 2025 income from freelance work (3.3% withholding), side jobs, and sole proprietorships — all must be reported. Using Hometax’s Modu-Chaeum (auto-fill) service, most filers can complete the process in under 10 minutes. Failure to file triggers a penalty of up to 40% of tax owed.

5 Categories of Filers — Do I Need to File?

Korea income tax filer categories freelancer side job sole proprietor rental
Figure 2. Five filer categories checklist
  1. Freelancers / personal service providers: Anyone with 3.3% withholding income — tutors, writers, designers, developers, etc.
  2. Salaried workers with side income: Financial, business, or miscellaneous income exceeding 3 million KRW per year beyond salary.
  3. Sole proprietors: All business owners with business income, regardless of industry.
  4. Rental income earners: Residential rental income up to 20 million KRW can choose separate taxation or aggregate filing.
  5. Financial income aggregate taxation: Interest and dividend income exceeding 20 million KRW annually triggers aggregate taxation.

5 Filing Methods — Modu-Chaeum Is Easiest (10 Minutes)

Korea income tax filing methods Hometax Modu-Chaeum Sontax tax agent
Figure 3. Five filing method comparison
  1. Hometax Modu-Chaeum (recommended): hometax.go.kr → File/Pay → Income Tax → Modu-Chaeum. NTS pre-fills income and deductions. Done in 10 minutes.
  2. Sontax mobile app: Sontax app → Income Tax Filing. Modu-Chaeum available on mobile too.
  3. Hometax standard filing: Manually enter income and deductions. Best for complex business income or multiple income sources.
  4. Tax agent (세무사): Recommended for annual revenue over 100M KRW or complex tax situations. Fee: 200,000–500,000 KRW.
  5. Tax apps (Samsam33, Toss): Specialized for 3.3% refund recovery. Suitable for simple freelancer filing. Fee: 10–20% of refund amount.

2025 Tax Rate Table — 8-Tier Progressive Rates (6–45%)

Korea income tax rate table 2025 8-tier progressive 6-45%
Figure 4. 2025 income tax 8-tier progressive rate table

The 2025 progressive income tax rates range from 6% to 45% across 8 tiers. Taxable income up to 14 million KRW: 6% → up to 50 million: 15% → up to 88 million: 24% → up to 150 million: 35% → up to 300 million: 38% → up to 500 million: 40% → up to 1 billion: 42% → over 1 billion: 45%. Rates apply progressively by bracket — at 50 million KRW income, only the amount above 14 million is taxed at 15%, not the full amount.

Flat Expense Ratio vs Standard Expense Ratio — Key for Business Owners

Korea income tax flat expense ratio standard expense ratio comparison sole proprietor
Figure 5. Flat expense ratio vs standard expense ratio comparison

Business owners without bookkeeping use expense ratios to estimate income. Flat expense ratio (단순경비율): applies to new businesses or small-scale operators below revenue thresholds. Industry-specific rate (40–90%) applied to gross revenue → taxable income = revenue × (1 – flat rate). Standard expense ratio (기준경비율): applies to higher-revenue businesses. Major expenses (purchases, wages, rent) deducted with receipts; the remainder uses the standard rate. The flat rate is often more tax-efficient — confirm eligibility first.

Hometax Self-Filing: 7-Step Guide to Finish in 10 Minutes

Hometax income tax self-filing 7 steps Modu-Chaeum
Figure 6. Hometax 7-step self-filing guide
  1. Go to hometax.go.kr → log in with certificate or easy authentication
  2. File/Pay → Tax Filing → Income Tax → Modu-Chaeum Filing
  3. Review auto-filled income (employment, business, miscellaneous income auto-retrieved)
  4. Confirm and add deductions (dependents, insurance, medical, education, donations)
  5. Review calculated tax → confirm refund amount or additional tax owed
  6. Submit return → save receipt
  7. If additional tax owed: pay by June 1 via virtual account, credit card, or internet banking

Hometax Screen Walkthrough

Hometax income tax filing main screen Modu-Chaeum
Figure 7. Hometax main screen
Hometax Modu-Chaeum filing screen income deduction auto-fill
Figure 8. Modu-Chaeum screen — auto-filled income and deductions
Hometax income tax deduction input screen
Figure 9. Deduction entry screen
Hometax income tax filing complete receipt screen
Figure 10. Filing complete — receipt screen

Refund vs Additional Payment Simulation — 4 Case Studies

Korea income tax refund additional payment simulation freelancer side job sole proprietor
Figure 11. Refund vs additional payment simulation — 4 cases

Case 1 — Freelancer earning 30M KRW (3.3% withheld): Tax withheld 990,000 KRW; with flat expense ratio, taxable income ~10M KRW, tax owed ~600,000 KRW → refund ~390,000 KRW. Case 2 — Salaried worker with 5M KRW side income: Separate taxation at 20% = 1,000,000 KRW; aggregate with salary depends on marginal rate — may result in refund or additional payment. Case 3 — Sole proprietor with 100M KRW revenue (standard ratio): Taxable income ~40M KRW, tax ~4,500,000 KRW → after provisional tax credit, may owe or receive refund. Case 4 — Rental income 15M KRW: Separate tax (14%) = 2,100,000 KRW vs aggregate — separate rate preferable with no other income.

5 Penalties for Non-Filing — Surcharges + Lost Refunds

Korea income tax non-filing penalties surcharges 5 consequences
Figure 12. 5 penalties for non-filing
  1. Non-filing surcharge: 20% of tax owed (40% for fraudulent non-filing)
  2. Late payment surcharge: 0.022% per day × days unpaid (approx. 8% annually)
  3. Forfeited refund: No refund without filing — though an amended return within 5 years is possible, it’s cumbersome
  4. Tax audit risk: Non-filing history increases likelihood of being selected for future tax audits
  5. Financial/administrative disadvantages: No income proof → restricted loan approval and government benefit eligibility

June 1 Deadline D-12 Action Playbook

Korea income tax June 1 deadline D-12 action playbook Hometax filing
Figure 13. June 1 deadline D-12 action playbook
  1. Today: Log in to hometax.go.kr → open Modu-Chaeum filing → confirm eligibility (5 minutes)
  2. If Modu-Chaeum eligible: Review income and deductions → submit immediately if refund → refund arrives in 3–4 weeks
  3. If standard filing required: Organize expense receipts → check flat vs standard ratio benefit → file
  4. If tax agent needed: Decide by May 28 (agents are fully booked near the deadline)
  5. June 1 payment: Refunds deposit automatically after filing / additional tax must be paid before midnight June 1
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