Korea Corporate Tax Compliance Calendar 2026: Essential Deadlines for Foreign Companies

Table of Contents

Introduction: Navigating Korea’s Tax Compliance Landscape

For foreign companies operating in Korea, tax compliance involves more than just filing an annual corporate income tax return. Korea’s National Tax Service (NTS) requires multiple filings throughout the year—covering corporate income tax, value-added tax (VAT), withholding taxes, and local taxes.

Missing deadlines can result in:

• Late filing penalties (10-20% of unpaid tax)
• Late payment surcharges (0.025% per day, up to 9% annually)
• Reduced credibility with tax authorities
• Potential immigration issues (clean tax records required for visa extensions)

This comprehensive 2026 Tax Compliance Calendar provides foreign businesses with all essential deadlines, filing requirements, and practical tips to maintain perfect tax compliance in Korea.

2026 Tax Year Overview: Key Dates by Tax Type

Before diving into month-by-month deadlines, here’s a summary of Korea’s main tax filing cycles:

Important Note: This calendar assumes a December 31 fiscal year-end, which is standard for most Korean companies. If your company has a different fiscal year-end (e.g., June 30 or September 30), adjust dates accordingly.

Month-by-Month 2026 Tax Compliance Calendar

January 2026

January 10, 2026 (Friday)

Withholding Tax on Employee Salaries (December 2025)

• Who: All companies with employees
• What: Income tax withheld from December salaries
• Where: Hometax (www.hometax.go.kr) or via tax agent
• Form: Withholding tax return (원천징수이행상황신고서)
• Amount: Based on employee income tax brackets and withholding tables

January 25, 2026 (Monday)

VAT Return (Q4 2025: October-December)

• Who: All VAT-registered businesses
• What: Quarterly VAT return for Q4 2025
• Where: Hometax or via tax agent
• Forms:
  • VAT return (부가가치세 신고서)
  • Purchase/sales invoices summary
• Payment: Net VAT payable (output VAT - input VAT)
• Refund: If input VAT > output VAT, file for refund

Tip: Ensure all December purchase invoices are collected before this deadline to maximize input VAT deductions.

January 31, 2026 (Saturday) → Extended to February 2, 2026 (Monday)

Semi-Annual Withholding Tax Return (Non-Employee Income, July-December 2025)

• Who: Companies making payments to non-employees (freelancers, contractors, royalties, interest)
• What: Consolidated withholding tax on non-employment income for H2 2025
• Rate: Varies by income type (3.3% for professional services, 22% for dividends, etc.)
• Forms:
  • Semi-annual withholding tax return
  • Individual payment records (지급명세서)

February 2026

February 10, 2026 (Tuesday)

Withholding Tax on Employee Salaries (January 2026)

• Same process as January 10 deadline above

February 28, 2026 (Saturday) → Extended to March 2, 2026 (Monday)

Annual Withholding Tax Reconciliation (연말정산)

• Who: All companies with employees
• What: Annual reconciliation of employee income tax for 2025
• Process:
  1. Collect employee deduction documents (medical expenses, education, donations, etc.)
  2. Calculate final tax liability for each employee
  3. Reconcile with taxes withheld throughout 2025
  4. Refund excess or collect shortfall
  5. Submit reconciliation report to NTS

Forms:

• Annual withholding tax reconciliation statement (근로소득 원천징수영수증)
• Employee-by-employee tax summaries
• Supporting documentation

Employee Documents Deadline: Typically mid-January (give employees 4-6 weeks to submit)

March 2026

March 10, 2026 (Tuesday)

Withholding Tax on Employee Salaries (February 2026)

• Standard monthly deadline

March 31, 2026 (Tuesday)

Business Registration Tax (for companies established in January)

• Who: Companies registered in January 2026
• What: One-time business registration tax
• Rate: Varies by region (typically 0.4% of capital)
• Where: Local tax office (지방세)

Note: This is a local tax, not national tax. Paid to the district/city office where business is registered.

April 2026

April 10, 2026 (Friday)

Withholding Tax on Employee Salaries (March 2026)

• Standard monthly deadline

April 25, 2026 (Saturday) → Extended to April 27, 2026 (Monday)

VAT Return (Q1 2026: January-March)

• Who: All VAT-registered businesses
• What: Quarterly VAT return for Q1 2026
• Process: Same as January VAT filing
• Common Issues:
  • Ensure all March invoices collected
  • Reconcile cash register sales
  • Verify electronic tax invoice issuance

Special Note for Foreign Companies:

• Cross-border services provided to Korean customers may be subject to reverse-charge VAT
• If you receive services from abroad, you may need to self-assess VAT

May 2026

May 10, 2026 (Sunday) → Extended to May 11, 2026 (Monday)

Withholding Tax on Employee Salaries (April 2026)

• Standard monthly deadline

May 31, 2026 (Sunday) → Extended to June 1, 2026 (Monday)

Comprehensive Real Estate Tax Declaration

• Who: Companies owning high-value real estate
• What: Declaration of real estate holdings as of June 1
• Threshold: Properties valued above KRW 600 million (residential) or KRW 4 billion (commercial/land)
• Relevance: Limited for most foreign SMEs, but important for real estate holding companies

June 2026

June 10, 2026 (Wednesday)

Withholding Tax on Employee Salaries (May 2026)

• Standard monthly deadline

No Major Tax Deadlines

July 2026

July 10, 2026 (Friday)

Withholding Tax on Employee Salaries (June 2026)

• Standard monthly deadline

July 25, 2026 (Saturday) → Extended to July 27, 2026 (Monday)

VAT Return (Q2 2026: April-June)

• Who: All VAT-registered businesses
• What: Quarterly VAT return for Q2 2026
• Midyear Review: Good time to review YTD VAT position and adjust invoicing practices if needed

July 31, 2026 (Friday)

Semi-Annual Withholding Tax Return (Non-Employee Income, January-June 2026)

• Who: Companies paying freelancers, contractors, royalties, etc.
• What: H1 2026 non-employee withholding tax return
• Forms: Same as January 31 filing

Property Tax (1st Installment)

• Who: Companies owning real estate (land, buildings)
• What: First half of annual property tax
• Rate: Varies by property type and value
• Where: Local tax office

August 2026

August 10, 2026 (Monday)

Withholding Tax on Employee Salaries (July 2026)

• Standard monthly deadline

August 31, 2026 (Monday)

Interim Corporate Income Tax Return

• Who: All companies (with some exceptions for small businesses)
• What: Tax return covering first 6 months of fiscal year (January-June 2026 for calendar-year companies)
• Calculation:
  • Option 1: Actual income method (calculate profit for Jan-Jun, apply tax rates)
  • Option 2: Provisional payment (50% of prior year’s total tax)
• Forms:
  • Interim corporate income tax return
  • Financial statements (simplified)
  • Supporting schedules

Tip: Most companies choose Option 2 (provisional payment) for simplicity, unless H1 performance was significantly worse than prior year (then Option 1 may reduce tax burden).

Local Income Tax (Interim)

• Filed concurrently with interim corporate tax
• Rate: 10% of national corporate tax amount

September 2026

September 10, 2026 (Thursday)

Withholding Tax on Employee Salaries (August 2026)

• Standard monthly deadline

September 30, 2026 (Wednesday)

Property Tax (2nd Installment)

• Who: Companies owning real estate
• What: Second half of annual property tax
• Note: This covers the balance of annual property tax (July payment was first installment)

October 2026

October 10, 2026 (Saturday) → Extended to October 13, 2026 (Tuesday)

Withholding Tax on Employee Salaries (September 2026)

• Standard monthly deadline

October 25, 2026 (Sunday) → Extended to October 26, 2026 (Monday)

VAT Return (Q3 2026: July-September)

• Who: All VAT-registered businesses
• What: Quarterly VAT return for Q3 2026
• Year-End Prep: Start planning for year-end tax optimization (accelerate/defer invoices if needed)

November 2026

November 10, 2026 (Tuesday)

Withholding Tax on Employee Salaries (October 2026)

• Standard monthly deadline

No Major Tax Deadlines

Action Item: Begin preparing for year-end financial closing and annual corporate tax return.

December 2026

December 10, 2026 (Thursday)

Withholding Tax on Employee Salaries (November 2026)

• Standard monthly deadline

Year-End Tax Planning

• Review 2026 P&L and identify tax optimization opportunities:
  • Accelerate deductible expenses (pay bonuses, prepay rent, etc.)
  • Defer taxable income (delay invoicing if possible)
  • Maximize R&D tax credits (ensure documentation complete)
  • Review transfer pricing compliance (for multinational groups)

Prepare for Annual Reconciliation

• Notify employees to prepare deduction documents for February 2027 reconciliation
• Audit payroll records for accuracy

2027 Q1 Deadlines (For 2026 Fiscal Year)

January 10, 2027

• Withholding tax on December 2026 salaries

January 25, 2027

• VAT return for Q4 2026

January 31, 2027

• Semi-annual withholding tax (non-employee, H2 2026)

February 28, 2027 (extended to March 2, 2027)

• Annual withholding tax reconciliation for 2026

March 31, 2027

Annual Corporate Income Tax Return (2026 Fiscal Year)

• Who: All companies
• What: Final corporate income tax return for fiscal year ending December 31, 2026
• Process:
  1. Finalize audited financial statements (if audit required)
  2. Prepare detailed tax schedules (revenue, expenses, adjustments)
  3. Calculate taxable income
  4. Apply tax rates and credits
  5. Submit return and pay balance due (or receive refund)

Forms:

• Corporate income tax return (법인세 신고서)
• Financial statements (income statement, balance sheet, cash flow)
• Supporting schedules (dozens of attachments depending on complexity)
• Disclosure of international transactions (for multinationals)

Local Income Tax (Annual)

• Filed concurrently with annual corporate tax
• Rate: 10% of national corporate tax

AGM Requirement: Corporations must hold Annual General Meeting within 3 months of FYE to approve financial statements before filing tax return.

Special Considerations for Foreign Companies

1. Transfer Pricing Documentation

Who: Companies with related-party transactions exceeding KRW 50 billion annually (or KRW 10 billion for specific transaction types)

What: Maintain contemporaneous transfer pricing documentation proving arm’s-length pricing

Deadline: Prepare during fiscal year; submit upon tax authority request

Penalties: Significant penalties for non-compliance or insufficient documentation

Action: Engage transfer pricing specialists if thresholds apply

2. Permanent Establishment (PE) Considerations

Issue: Foreign companies with PE in Korea (e.g., branch offices, construction sites >12 months, dependent agents) must file Korean corporate tax returns

Impact: Even without a Korean subsidiary, PE creates Korean tax liability on profits attributable to PE activities

Advice: Consult tax advisors on PE risk if operating in Korea without a registered entity

3. Dividend Withholding Tax

Trigger: When Korean subsidiary distributes dividends to foreign parent

Rate:

• Default: 22% (14% national + 1.4% local + 6.6% additional)
• Treaty-reduced: Typically 5-15% depending on country

Process:

1. Board approves dividend
2. Shareholders approve at AGM
3. Company withholds tax on gross dividend
4. Company remits net dividend to foreign parent
5. Company files withholding tax return

Deadline: By 10th of month following dividend payment

Treaty Relief: Must submit treaty application forms to NTS before dividend payment to benefit from reduced rate

4. R&D Tax Credits

Opportunity: Foreign companies conducting R&D in Korea may qualify for significant tax credits

Types:

• General R&D credit: 0-50% of qualifying R&D expenses (rate varies by company size)
• Increase in R&D credit: Up to 40% of year-over-year R&D increase
• New Growth Engine R&D credit: Up to 20-40% for specified technologies (AI, biotech, etc.)

Documentation:

• Detailed R&D project descriptions
• Separation of R&D vs. non-R&D expenses
• Technical reports proving innovation

Action: Consult with tax advisors Q1-Q3 to maximize credit claims in annual return

5. Country-by-Country Reporting (CbCR)

Who: Korean subsidiaries of multinational groups with consolidated revenue >KRW 1 trillion (approx. USD $750 million)

What: Report global allocation of income, taxes, and economic activities by jurisdiction

Deadline: 12 months after end of parent company’s fiscal year

First Filing: Many companies had first filings in 2024-2025 for 2023 FY; ensure ongoing compliance in 2026

6. OECD Pillar Two (Global Minimum Tax)

New in 2024-2026: Korea implemented OECD Pillar Two, imposing 15% global minimum tax on large multinationals

Who: Multinational groups with consolidated revenue >EUR €750 million

What:

• Income Inclusion Rule (IIR): Top-up tax if subsidiaries in low-tax jurisdictions
• Qualified Domestic Minimum Top-Up Tax (QDMTT): Korea charges top-up tax on Korean entities if effective rate <15%

GloBE Information Return: First submissions due June 2026 for 2024 fiscal year (for affected groups)

Action: Large multinationals must engage Big 4 firms for Pillar Two compliance

Penalties for Late Filing or Non-Compliance

Understanding penalty structures helps prioritize compliance:

Corporate Income Tax

VAT

Withholding Tax

Additional Consequences

• Visa implications: Clean tax records required for D-8 visa renewals; non-compliance can delay or prevent extensions
• Bank financing: Korean banks review tax compliance; poor records limit access to loans
• M&A issues: Tax non-compliance discovered in due diligence drastically reduces valuation or kills deals
• Reputation damage: Tax authorities may publicize serious violations

Best Practices for Tax Compliance

1. Implement a Tax Compliance Tracking System

Tool Options:

• Excel calendar with automated reminders (simple)
• Accounting software with tax deadline features (mid-tier)
• Full ERP systems with tax modules (enterprise)

Minimum: Recurring calendar invites 2 weeks before each deadline

2. Engage a Korean Tax Agent

Why:

• Navigate Hometax system (Korean language interface)
• Ensure proper form completion
• Monitor regulatory changes
• Represent you in tax audits

Cost:

• Basic filing services: KRW 300,000-1,000,000 per filing
• Full-service annual retainer: KRW 5,000,000-20,000,000

When to Hire:

• If no Korean-speaking staff internally
• If business exceeds KRW 1 billion revenue
• If any cross-border transactions or transfer pricing issues

3. Reconcile Accounts Monthly

Don’t wait until filing deadlines:

• Monthly bank reconciliation: Catch errors early
• Monthly VAT tracking: Monitor input/output VAT ratios
• Quarterly profit review: Anticipate tax liabilities and plan cash flow

4. Maintain Organized Records

VAT:

• Electronic tax invoice copies (legally required)
• Purchase receipts and invoices
• Justification for input VAT claims

Corporate Tax:

• General ledger and trial balance
• Expense receipts and approvals
• Payroll records and employment contracts
• Bank statements
• Related-party transaction documentation

Retention Period: 5 years minimum (10 years for certain documents)

5. Plan for Year-End from Day One

Quarterly Reviews:

• Q1: Confirm accounting policies, review R&D credit eligibility
• Q2: Adjust estimated tax provisions
• Q3: Identify year-end tax optimization strategies
• Q4: Execute optimizations, finalize documentation

6. Leverage Technology

Hometax e-Filing: Mandatory for most businesses; familiarize staff or agent with platform

Electronic Tax Invoices: Required for most B2B transactions; integrate with accounting system

Automation: Modern accounting software can auto-generate VAT returns and withholding reports

7. Conduct Internal Audits

Annually: Review prior year filings for accuracy and optimization opportunities

Common Findings:

• Missed deductions
• Overpaid VAT (unclaimed input credits)
• Transfer pricing weaknesses
• Underutilized tax credits

ROI: Internal audits often identify KRW 10-50 million in tax savings for mid-sized companies

Tax Compliance Checklist for Foreign Companies

Use this checklist to ensure comprehensive compliance:

Monthly

• File withholding tax on employee salaries (by 10th)
• Reconcile bank accounts
• Track input/output VAT
• Review expense approvals

Quarterly

• File VAT return (by 25th of month following quarter)
• Review quarterly P&L
• Adjust tax provisions
• Pay estimated taxes if required

Semi-Annually

• File non-employee withholding tax return (Jan 31, Jul 31)
• File interim corporate tax return (Aug 31)
• Pay property tax (if real estate owned) (Jul 31, Sep 30)

Annually

• Annual withholding tax reconciliation (Feb 28)
• Annual corporate tax return (Mar 31 following FYE)
• Annual general meeting for corporations (within 3 months of FYE)
• Prepare audited financials (if required)
• File transfer pricing documentation (if applicable)
• Review tax credits and incentives
• Plan next year’s tax strategy

As Needed

• Business registration upon establishment
• Dividend withholding when paying dividends
• Tax treaty benefit applications
• Transfer pricing studies (every 3-5 years)

Conclusion: Staying Ahead of Korean Tax Deadlines

Tax compliance in Korea demands proactive planning, organized record-keeping, and timely filings. For foreign companies, the complexity is amplified by language barriers, unfamiliar systems, and cross-border considerations.

Key Takeaways:

1. Mark These Recurring Deadlines: 10th (withholding), 25th (VAT), 31st (semi-annual), March 31 (annual)
2. Budget for Professional Help: Tax agents are not optional for most foreign SMEs
3. Maintain Immaculate Records: Digital organization saves countless hours during filings
4. Plan Year-End Early: Tax optimization happens throughout the year, not just in December
5. Stay Current on Regulatory Changes: Korea’s tax landscape evolves; monitor NTS announcements

With this 2026 Tax Compliance Calendar, foreign companies can navigate Korea’s tax obligations confidently, avoid costly penalties, and maintain the clean compliance record essential for long-term success in the Korean market.

Get Professional Tax Compliance Support

Managing Korean tax compliance while running your core business is challenging. SMA Lawfirm offers comprehensive tax and accounting services for foreign companies, including:

• Monthly withholding tax filing and remittance
• Quarterly VAT return preparation and submission
• Annual corporate tax return preparation and strategy
• Tax optimization consulting (R&D credits, treaty benefits, transfer pricing)
• Hometax account setup and ongoing support
• Audit representation if selected for NTS review
• Bilingual support (Korean-English) for seamless communication

📩 Contact us at sma@saemunan.com to discuss your tax compliance needs and receive a customized service proposal.

Disclaimer: This calendar provides general information about Korean tax deadlines as of February 2026. Tax laws and regulations are subject to change. Always consult qualified tax professionals for advice specific to your company’s circumstances.