Self Employed Tax in South Korea

What statutory framework governs Korean self-employed taxation?

South Korean self-employed individuals register as sa-eob-so-deuk-ja (사업소득자 — business-income earners) by filing Business Registration Certificate Application (saeobja deunglokjeung sincheongseo 사업자등록증신청서) with the local NTS office within 20 days of business commencement. The So-deuk-se-beob (소득세법 — Income Tax Act, Act 4519 of 1949) governs personal income taxation including business-income calculation, supplemented by the Ji-bang-se-beob (지방세법 — Local Tax Act) for the 10% local income tax surcharge. Net business income — gross revenue minus documented business expenses — flows through the progressive personal income tax schedule across 8 bands ranging from 6% to 45%. The National Tax Service (Kuk-se-cheong 국세청 — NTS) administers personal income taxation while local-government tax offices administer the local-income-tax surcharge. PwC's 2026 South Korea tax summary identifies the Korean framework as among Asia's most progressive — the 45% national top rate plus 10% local surcharge produces a 49.5% combined effective top rate, materially higher than Singapore's 24% top, Hong Kong's 17% top, or Taiwan's 40% top.

What are the progressive Korean tax bands?

The So-deuk-se-beob establishes an 8-band progressive personal income tax schedule covering business and employment income. Bands (all KRW, 2026 thresholds): 6% on the first ₩14 million; 15% to ₩50 million; 24% to ₩88 million; 35% to ₩150 million; 38% to ₩300 million; 40% to ₩500 million; 42% to ₩1 billion; 45% above ₩1 billion. The local income tax surcharge under the Ji-bang-se-beob applies at 10% of the national income tax payable, producing effective combined rates of 6.6% (lowest band) to 49.5% (top band). KPMG's 2026 South Korea personal-tax profile reports the Korean rate structure substantially escalates above the ₩88 million threshold, with median full-time-employed Koreans typically falling in the 15-24% national bracket. EY's 2026 commentary identifies the band structure as particularly burdensome for high-earning independent professionals (doctors, lawyers, IT consultants) frequently exceeding the ₩150 million threshold where 35% national plus 10% surcharge produces effective marginal rates approaching 38%.

How does simplified-bookkeeping (gan-pyeon-jang-bu) work?

The simplified-bookkeeping framework (gan-pyeon-jang-bu 간편장부) under Section 70 of the So-deuk-se-beob provides smaller sa-eob-so-deuk-ja with reduced compliance burden. Eligibility thresholds vary by business category: services category (consulting, professional services, IT) qualifies up to ₩75 million annual revenue; manufacturing and construction qualifies up to ₩150 million; wholesale qualifies up to ₩300 million; retail qualifies up to ₩100 million; most other categories qualify up to ₩36 million. Above the relevant threshold, full double-entry bookkeeping (bok-sik-jang-bu 복식장부) is mandatory with detailed ledger documentation, financial-statement preparation, and broader audit-trail requirements. The simplified framework permits expense recognition based on simplified-rate calculations or actual documentation, reducing administrative burden substantially for qualifying small operators. KPMG's 2026 Korea commentary identifies the simplified-vs-full bookkeeping election as the principal compliance-burden lever for growing Korean sole proprietors. The Korean small-business crossover at /global/jurisdictions/country/kr/topic/small-business-tax covers the alternative corporate-vehicle (juseokhwesa 주식회사) framework offering preferential SME corporate-tax rates.

What VAT framework applies to sole proprietors?

Korean Value-Added Tax (Bu-ga-ga-chi-se 부가가치세 — VAT) under the Bu-ga-ga-chi-se-beob (Value-Added Tax Act) applies at 10% standard rate to most goods and services. Mandatory VAT registration triggers at ₩48 million annual revenue threshold under Article 10 — substantially lower than the Japanese ¥10 million (~₩89 million) threshold. Below the threshold, the simplified VAT framework (gan-iyo bu-ga-ga-chi-se 간이부가가치세) applies a reduced rate structure (0.5% to 3% depending on business category) replacing standard input-output VAT calculation. Above ₩48 million, full VAT obligations apply: quarterly VAT returns, e-tax-invoice (jeon-ja-se-geum-gye-san-seo 전자세금계산서) issuance for B2B transactions above ₩30 million annual revenue, and full input-tax-credit calculation. Korean electronic-invoicing under the NTS Hometax mandate is substantially more developed than most OECD peers — practically all VAT-registered Korean businesses use electronic invoicing through the Hometax portal or integrated accounting software. EY's 2026 Korea VAT commentary identifies the lower registration threshold as a significant compliance burden for inbound foreign professionals who quickly exceed the threshold even at modest service-business scale.

What social-security contributions apply?

Korean sole proprietors face mandatory social-security contributions under four principal schemes. National Pension (Kuk-min-yeon-geum 국민연금): 4.5% of declared income up to the contribution ceiling (approximately ₩5.9 million monthly base in 2026). Self-employed individuals pay only the employee-equivalent 4.5% rather than the combined 9% paid by employed persons. National Health Insurance (Kuk-min-geon-gang-bo-heom 국민건강보험): approximately 6.99% calculated on household-income-based formula combining business income with other household income — Korean NHI uses a complex calculation that often produces higher contributions than simple percentage-of-income tracking. Long-Term Care Insurance (Jang-gi-yo-yang-bo-heom 장기요양보험): 0.79% addition to NHI. Employment Insurance (Go-yong-bo-heom 고용보험): 0.9% if sole proprietor elects voluntary participation. Total combined contributions: approximately 13% for typical sole proprietors. PwC's 2026 Korea social-security commentary notes the household-income-based NHI calculation as a frequent practitioner complication — Korean spousal-household income aggregation can produce unexpected contribution increases. The Korean expat-tax crossover at /global/jurisdictions/country/kr/topic/expat-tax-residency covers inbound expat coverage including social-security totalisation agreements.

Can foreign self-employed elect the flat-19% framework?

No — the flat 19% foreign-employee inbound election under Article 18-2 of the Special Tax Treatment Limitation Act (Jo-se-teug-rye-je-han-beob 조세특례제한법 — STTLA) applies only to employed persons, not self-employed. Self-employed foreign nationals operating in Korea must use the standard Income Tax Act framework with the 6-45% progressive rates plus 10% local surcharge. The 5-year residency-relief framework under Section 3 of the STTLA partially mitigates inbound exposure: foreign individuals classified as Korean residents for fewer than 5 of the 10 preceding years face Korean income tax only on Korean-source income (similar to Japanese NPR framework but without the remittance trigger). High-earning foreign professionals frequently consider incorporation strategies — establishing a Korean corporate vehicle (juseokhwesa) accessing the SME-preferential 9% effective rate on the first ₩200 million corporate income discussed in the Korean small-business crossover at /global/jurisdictions/country/kr/topic/small-business-tax. The Korean expat-tax crossover at /global/jurisdictions/country/kr/topic/expat-tax-residency covers the 5-year residency-relief framework in detail.

How do international filers handle won conversion and cross-border billing?

Korean sa-eob-so-deuk-ja invoicing in foreign currencies must convert to Korean won (KRW) at the Korea Exchange Bank (Han-guk-eun-haeng 한국은행) telegraphic-transfer middle rate (TTM) on invoice date for income-tax recognition under Article 24 of the So-deuk-se-beob. Cross-border foreign-currency invoice and bank-account management runs through WorldFirst with cost-effective EUR/USD/GBP to KRW conversion supporting sa-eob-so-deuk-ja working with foreign clients. US-platform 1099 reconciliation for Korean-resident sa-eob-so-deuk-ja flows through services like Tax1099 supporting accurate cross-border income reporting. Korean Hometax electronic-filing system requires online submission of annual personal income tax return (jong-hap-so-deuk-se sin-go 종합소득세 신고) by 31 May following the tax year. The Korean tax-treaty crossover at /global/jurisdictions/country/kr/topic/tax-treaty-relief covers Korea's 95+ DTA framework supporting cross-border source-state withholding reductions.

What compliance and recordkeeping obligations apply?

NTS requires sa-eob-so-deuk-ja to retain accounting records for 5 years from the close of the fiscal year (10 years for VAT-relevant documentation) under the National Tax Basic Act (Kuk-se-gi-bon-beob 국세기본법). Required documents: e-tax-invoices issued and received through Hometax, sales records, banking statements, social-security contribution declarations, and VAT return calculations where applicable. Annual personal income tax return (jong-hap-so-deuk-se sin-go) is due 31 May following the tax year. VAT returns due quarterly (April, July, October, January) for fully-registered businesses. Late-filing penalties under the National Tax Basic Act reach 0.5% per day plus interest at 4% per annum compounded. Practitioners commonly recommend Korean Certified Tax Accountants (Se-mu-sa 세무사) registered with the Korean Association of Certified Public Tax Accountants for complex sa-eob-so-deuk-ja structuring including simplified-vs-full bookkeeping election analysis, VAT-registration optimisation, social-security contribution planning, and incorporation-vs-sole-proprietor analysis.