End-to-end workflow for a Korean resident sole proprietor to prepare and file the annual Comprehensive Income Tax return (종합소득세 신고서) via Hometax by the 31 May deadline, covering 3.3% withholding gross-up, bookkeeping method selection, 소득공제 deductions, local income tax (지방소득세), and 중간예납 credit reconciliation.
Confirm the taxpayer is a Korean resident individual (거주자) filing as a sole proprietor, not a corporation or non-resident. Identify the business type code (업종코드), the tax year in scope, and any refusal triggers (foreign income, financial income > KRW 20M, real estate gains) that require escalation before proceeding.
Collect all bank statements (KB국민, 신한, 하나, 우리, 카카오뱅크, 토스뱅크, etc.) and digital platform settlement reports (Naver Pay, KakaoPay, Coupang). Identify every business income credit, gross up all net-of-withholding amounts to the full invoice value (3.3% = 3% national + 0.3% local), and reconcile against withholding receipts (원천징수영수증) issued by corporate clients.
Classify all business debit transactions into NTS expense categories (임차료, 통신비, 여비교통비, 접대비, 소모품비, 외주비, etc.), apportion home-office and mixed-use items, apply the entertainment cap (접대비), and determine whether actual-cost bookkeeping (간편장부 or 복식부기) or the standard deduction rate (기준경비율 / 단순경비율) produces the lower taxable income. Double-entry bookkeeping (복식부기) is mandatory if revenue exceeds KRW 75,000,000 for service businesses.
Identify and quantify all income-level deductions available to the taxpayer: basic personal deduction (기본공제 KRW 1.5M per person), dependent deductions, national pension premiums (국민연금), national health insurance premiums (국민건강보험), and employment insurance (고용보험). These are deducted from total income (종합소득금액) to arrive at taxable income (과세표준) and must not be recorded as business expenses.
Apply the national income tax rate table to the taxable income (과세표준), add the 10% local income tax surtax (지방소득세), then subtract all credits: the standard credit (표준세액공제 KRW 70,000), child tax credit, withholding credits (원천징수 3.3%), and any 중간예납 (estimated tax) already paid in November. Produce the final tax due or refund.
Prepare and submit the 종합소득세 신고서 via the NTS Hometax portal (hometax.go.kr) by 31 May. Attach supporting schedules (income statement, deduction certificates, withholding receipts). Arrange payment of any balance due by 31 May, or instalment arrangement if applicable. Confirm the 지방소득세 return is also filed separately with the local government via Wetax (wetax.go.kr) by the same deadline.
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