Thailand's 2026 Corporate Tax Changes: What Foreign-Owned Companies Need to Know

Thailand's Revenue Department has introduced a number of changes to corporate income tax (CIT) compliance that take effect for the 2026 tax year. For foreign-owned companies operating through a Thai limited company or BOI-promoted entity, several of these changes affect how you prepare accounts, file returns, and plan for year-end.

What's changed

• Updated SME tax brackets. Companies with paid-up capital not exceeding THB 5 million and revenue not exceeding THB 30 million continue to benefit from progressive CIT rates (0% / 15% / 20%), but the Revenue Department has tightened the documentation required to qualify — particularly around shareholding structure and related-party transactions.
• Stricter transfer pricing disclosure. Companies with related-party transactions above the existing threshold must now submit a more detailed disclosure form alongside the annual CIT return (form Por Ngor Dor 50), with additional fields covering cross-border service and royalty arrangements.
• e-Filing enforcement. Mid-sized and large companies are now required to file CIT returns and supporting schedules exclusively through the Revenue Department's e-filing portal — paper submissions are no longer accepted for entities above the SME threshold.
• Half-year (PND 51) reconciliation. The half-year estimate filed in PND 51 is now cross-checked more closely against the year-end PND 50 figure; a significant underestimate (beyond the existing 25% tolerance) can trigger a surcharge review automatically rather than only on audit.

Why this matters for foreign-owned businesses

Many foreign-owned SMEs in Thailand operate close to the SME CIT thresholds, and the tightened documentation requirements mean that a company's structure — including how shares are held by a foreign parent versus Thai nominees or partners — needs to be clearly evidenced in the company's records, not just in the registration filings from years ago.

For BOI-promoted companies, the corporate tax exemption period still applies as granted, but the non-exempt portion of activities (if your BOI certificate covers only part of your business) now needs to be reported with clearer segmentation in the supporting schedules.

What to do before your next filing

1. Review your shareholding and related-party map. If your group has cross-border management fees, royalties, or intercompany loans with Thailand, confirm these are documented with contracts and pricing rationale that would withstand a transfer pricing review.
2. Check your e-filing registration. If your company has historically filed on paper or through an accountant's manual submission, confirm your tax ID is properly registered for e-filing well before the deadline — registration can take several weeks.
3. Reconcile your half-year estimate early. Don't wait until year-end to compare your PND 51 estimate against actuals — a wide gap is now flagged faster.
4. Confirm your BOI activity segmentation, if applicable, so exempt and non-exempt income/expenses are cleanly separated in your management accounts.

How ATA can help

Our outsourcing team handles monthly bookkeeping, CIT and VAT filings, and BOI compliance reporting for foreign-owned companies across Thailand. If you're unsure whether these changes affect your filing for this year, get in touch with our accounting team for a quick compliance review — we can usually confirm your position within a few business days.