Thailand's corporate income tax system affects every business operating in the country, from multinational manufacturers to small service companies started by foreign entrepreneurs. Understanding how CIT works — the rates, the filing deadlines, the deductions, and the penalties for non-compliance — is not optional. Get it wrong and you face surcharges of 1.5 percent per month plus penalties up to 200 percent of the tax owed. Get it right and you can optimize your tax position legitimately, especially if your company qualifies for SME rates or BOI tax holidays. This guide covers every aspect of corporate income tax in Thailand for 2026 with the practical detail business owners actually need.
Standard Corporate Income Tax Rate
The standard corporate income tax rate in Thailand is 20 percent of net profit, applicable to all companies that do not qualify for SME rates or special incentives. This rate has been stable since 2012 when it was reduced from 23 percent, and no changes are expected in 2026. The tax applies to worldwide income for companies incorporated in Thailand and to Thailand-source income for foreign companies with a permanent establishment in the country.
Net profit is calculated as total revenue minus deductible expenses, after adjusting for non-deductible items and adding back non-taxable income that was incorrectly deducted. The computation follows Thai Financial Reporting Standards (TFRS), which are substantially aligned with IFRS but with some Thai-specific modifications that every accountant working in Thailand must understand.
SME Progressive Tax Rates
Small and medium enterprises registered in Thailand benefit from progressive tax rates that can significantly reduce their tax burden. To qualify as an SME, a company must have paid-up capital not exceeding 5 million THB at the end of each accounting period and must not receive annual income from the sale of goods or provision of services exceeding 30 million THB.
The SME progressive rates for 2026 are: 0 percent on the first 300,000 THB of net profit, 15 percent on net profit between 300,001 and 3,000,000 THB, and 20 percent on net profit exceeding 3,000,000 THB. This means a company with 2 million THB in net profit pays approximately 255,000 THB in CIT — an effective rate of about 12.75 percent — compared to 400,000 THB at the standard 20 percent rate.
The SME rates are particularly valuable during the early years of operation when profits are lower. A startup that earns 500,000 THB in its first year pays only 30,000 THB in CIT (15 percent on 200,000 THB after the 300,000 THB exemption). This progressive structure is one reason many foreign entrepreneurs initially register their companies with smaller capital amounts.
It is important to note that the SME status is evaluated annually. If your paid-up capital exceeds 5 million THB or your revenue crosses 30 million THB in any year, you lose SME status and must apply the standard 20 percent rate for that year.
Filing Deadlines and Forms
Thailand requires two types of corporate income tax filings during each fiscal year: the half-year return and the annual return.
**PND51 — Half-Year Corporate Income Tax Return:** This estimated tax return covers the first six months of the fiscal year or the first accounting period (whichever is shorter). PND51 must be filed within 2 months after the end of the first half of the accounting period. For companies with a fiscal year ending December 31, the half-year return covers January through June and must be filed by August 31. The tax due is calculated based on estimated net profit for the first half of the year. If your company estimates zero profit or a loss, you file PND51 showing zero tax due — but you must still file the return.
**PND50 — Annual Corporate Income Tax Return:** This is the definitive tax return for the full fiscal year. PND50 must be filed within 150 days after the last day of the accounting period. For a December 31 year-end, the filing deadline is May 30 of the following year. PND50 reports actual income, deductions, and the final tax liability. Any excess tax paid through PND51 is credited against the PND50 liability. If the PND50 liability exceeds what was paid through PND51, the balance must be paid with the annual return.
Both returns are filed electronically through the Revenue Department's e-filing system. Late filing triggers penalties and surcharges that compound quickly, making timely compliance essential.
Penalties for Non-Compliance
The Revenue Department enforces strict penalties for CIT non-compliance, and these penalties are applied consistently regardless of whether the failure was intentional.
**Late filing surcharge:** 1.5 percent per month (or fraction of a month) of the unpaid tax amount, capped at the tax due. This surcharge starts from the day after the filing deadline and accumulates monthly until payment is made.
**Late payment surcharge:** An additional 1.5 percent per month of the unpaid tax if you file on time but fail to pay the full amount. This runs in parallel with filing surcharges when both apply.
**Penalty for incorrect return:** If the Revenue Department assesses additional tax after an audit, the penalty ranges from 100 percent to 200 percent of the additional tax assessed, depending on whether the authority views the error as negligence or intentional evasion.
**Criminal penalties:** In cases of deliberate tax evasion, company directors can face criminal prosecution with fines and imprisonment of up to 7 years. While criminal prosecution is rare for first-time offenders with reasonable explanations, it is a real risk for companies that systematically underreport income.
The combination of surcharges and penalties means that a company owing 500,000 THB in CIT that files 6 months late and is found to have underreported by 200,000 THB could face total obligations exceeding 1.5 million THB. Compliance is always cheaper than non-compliance.
BOI Tax Holidays
Companies that receive BOI promotion can receive corporate income tax holidays of 3 to 13 years depending on their promoted activity and incentive tier. During the tax holiday period, the company pays zero CIT on income derived from the promoted activity. This is the most powerful tax incentive available in Thailand and can save promoted companies tens of millions of baht over the holiday period.
After the CIT holiday expires, many BOI-promoted companies qualify for a 50 percent CIT reduction for an additional period. The specific duration depends on the incentive tier. A company receiving an 8-year CIT holiday might also receive a 5-year 50 percent reduction, resulting in a 10 percent effective rate for years 9 through 13.
BOI-promoted companies must maintain separate accounting for promoted and non-promoted activities. Only income from promoted activities qualifies for the tax holiday. Non-promoted income is taxed at standard rates. The Revenue Department audits this separation carefully, and companies that commingle promoted and non-promoted revenue risk losing their tax holiday.
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Special Economic Zone Rate
Companies operating in Thailand's Special Economic Zones benefit from a reduced CIT rate of 10 percent, compared to the standard 20 percent. This rate applies to income derived from business activities conducted within the SEZ. The SEZ incentive is designed to attract investment to border provinces and less-developed areas of Thailand.
To qualify, the company must be registered to operate in a designated SEZ and conduct its core business activities within the zone. The 10 percent rate applies without time limitation as long as the company maintains its SEZ registration and operations.
Dividend Rules and Withholding Tax
Dividends paid by a Thai company to its shareholders are subject to withholding tax, but the rules include important exclusions that can reduce or eliminate the tax burden.
**Dividends between Thai companies:** If a Thai company receives dividends from another Thai company, 50 percent of the dividend is excluded from assessable income if the recipient has held at least 3,000 shares (or all shares if fewer than 3,000 exist) for at least 3 months before and after the dividend record date. If the recipient holds 25 percent or more of the paying company's total shares and has held them for at least 3 months before the record date, the dividends are fully exempt from corporate income tax.
**Dividends to foreign shareholders:** Dividends paid to non-resident foreign companies are subject to 10 percent withholding tax. This rate may be reduced under a double taxation agreement between Thailand and the recipient's country of residence. For example, the Thailand-Singapore DTA reduces the withholding rate to 10 percent, while the Thailand-Japan DTA reduces it to 10 percent for dividends paid to Japanese companies holding at least 25 percent of shares.
**Dividends to individual shareholders:** Thai individuals receiving dividends face 10 percent withholding tax, which serves as a final tax. Foreign individuals face the same 10 percent withholding, which may be creditable against tax in their home country under applicable DTAs.
Deductible vs Non-Deductible Expenses
Understanding which expenses are deductible and which are not is essential for accurate CIT computation.
**Deductible expenses** include salaries and wages (subject to withholding tax compliance), rent, utilities, office supplies, marketing and advertising costs, travel expenses for business purposes, depreciation of assets (with prescribed rates), bad debts written off (with documentation), interest expenses (subject to thin capitalization rules), insurance premiums, and charitable donations up to 2 percent of net profit (to approved organizations).
**Non-deductible expenses** include personal expenses of directors and shareholders, entertainment expenses exceeding prescribed limits, fines and penalties paid to government authorities, expenses without proper tax invoices, expenses related to non-business activities, provisions for anticipated losses (unless specifically permitted), and dividends paid to shareholders.
The Revenue Department requires that all deductible expenses be supported by proper documentation — tax invoices for amounts over 200 THB, receipts, contracts, and bank payment records. Expenses claimed without adequate documentation will be disallowed during audit, potentially triggering penalties.
Thai Financial Reporting Standards
All companies registered in Thailand must prepare financial statements in accordance with Thai Financial Reporting Standards. TFRS has been converging with IFRS since 2011, and most TFRS standards are now substantially aligned with their IFRS counterparts. However, differences remain in areas such as fair value measurement, financial instrument classification, and revenue recognition timing.
Companies must appoint a certified Thai auditor to audit their financial statements annually. The audited financial statements must be filed with the Department of Business Development within 5 months of the fiscal year-end (one month earlier than the CIT filing deadline). This means companies effectively have two filing deadlines close together — the DBD financial statement filing and the Revenue Department PND50 filing.
For foreign entrepreneurs accustomed to IFRS or US GAAP, the transition to TFRS is generally straightforward, but specific differences can affect how transactions are recorded and how profit is calculated for tax purposes. Working with an accountant experienced in both TFRS and your home country's standards helps ensure compliance and optimize your tax position.
The Compliance Calendar
Staying compliant requires attention to multiple deadlines throughout the year. For a company with a December 31 fiscal year-end, the key dates are: January 31 for VAT filing (monthly), February 28 for withholding tax filing (monthly, ongoing), April 30 for DBD financial statement filing, May 30 for PND50 annual CIT return, and August 31 for PND51 half-year CIT return. Monthly obligations include VAT filing by the 15th (or next business day) of the following month and withholding tax filing by the 7th (or next business day) of the following month.
Missing any of these deadlines triggers penalties and surcharges. The most expensive mistakes are usually the PND50 and PND51 filings because the surcharges are calculated on the tax amount owed. Setting up a compliance calendar and working with a qualified Thai accountant from the start of operations is not optional — it is fundamental to running a legitimate business in Thailand.
For entrepreneurs setting up in Chiang Mai or other cities outside Bangkok, the Revenue Department offices are equally capable and the filing requirements are identical. All major filings can be done electronically, so physical proximity to the Revenue Department is no longer a factor.
Final Recommendations
Every business in Thailand must understand and comply with CIT obligations. The system is not excessively complex, but the penalties for mistakes are severe enough to warrant professional support from the beginning. If your company qualifies for SME rates, make sure your accountant applies them correctly and monitors the qualification thresholds annually. If you are considering BOI promotion or choosing your company structure, factor the CIT implications into your decision. And if you are behind on filings or payments, address the issue immediately — the surcharges compound monthly and waiting only makes the problem worse.
