Thailand Tax Calendar 2026: Key Filing Deadlines Every Business Must Know

Staying on top of tax deadlines in Thailand is critical for every business, whether you are a local SME or a foreign-owned company. Missing a deadline can result in penalties, surcharges, and unwanted attention from the Revenue Department. This comprehensive guide outlines every key filing date for the 2026 tax year so you can plan ahead and remain fully compliant.

Monthly Obligations: Withholding Tax and VAT

Every company registered for VAT in Thailand must file a monthly VAT return (Por Phor 30) by the 15th of the following month. Similarly, withholding tax returns (Por Ngor Dor 3, 53, and 54) are due by the 7th of the following month. These are non-negotiable monthly obligations that apply throughout the year. Late filing attracts a surcharge of 1.5% per month on unpaid amounts, plus potential fines of up to 2,000 THB per occurrence.

Semi-Annual Corporate Income Tax (PND 51)

Thai companies must file a half-year corporate income tax return (PND 51) within two months after the end of the first six months of their accounting period. For companies with a fiscal year ending 31 December, the PND 51 deadline falls on 31 August. This return estimates the full-year profit and requires payment of half the estimated annual corporate income tax. Accurate forecasting at this stage helps avoid underpayment penalties later.

Annual Corporate Income Tax (PND 50)

The annual corporate income tax return (PND 50) must be filed within 150 days after the end of the accounting period. For a December year-end, this means the deadline is 31 May. The standard corporate income tax rate in Thailand is 20%, though SMEs meeting certain criteria may qualify for reduced rates. This filing requires audited financial statements prepared by a certified public accountant (CPA) registered with the Department of Business Development (DBD).

Social Security Contributions

Employers must remit social security contributions by the 15th of each month. The contribution rate is 5% from both employer and employee, capped at a maximum monthly salary of 15,000 THB. This means the maximum monthly contribution is 750 THB each from employer and employee. Consistent and timely remittance avoids penalties and ensures employees maintain their coverage.

Specific Business Tax (SBT)

Businesses subject to Specific Business Tax, including banks, insurance companies, and real estate developers, must file monthly SBT returns (Phor Thor 40) by the 15th of the following month. The tax rate varies by industry, typically ranging from 0.1% to 3.3% of gross receipts.

Annual Financial Statements and DBD Filing

All limited companies in Thailand must submit their audited financial statements to the DBD within five months after the end of their fiscal year. For companies with a December year-end, this means 31 May. These statements must be prepared in accordance with Thai Financial Reporting Standards (TFRS) and audited by a licensed CPA. The annual general meeting to approve these statements must be held within four months of the fiscal year-end.

How Arbor Thailand Can Help

Managing Thailand's complex tax calendar requires expertise and vigilance. At Arbor Thailand, our professional accounting team handles all monthly, semi-annual, and annual tax filings on your behalf. We ensure timely submission, accurate calculations, and full compliance with Thai tax regulations. Whether you need ongoing bookkeeping, payroll processing, or strategic tax planning, our team is here to support your business every step of the way. Contact us today to ensure you never miss a deadline.