Corporate income tax — the annual PND.50, the half-year PND.51, and foreign documents that need translation

A company files corporate income tax twice per accounting period. PND.51 is a half-year estimate of net profit with a payment on account. PND.50 is the annual return based on actual results. Tax paid with PND.51 and tax withheld at source are credited against the final liability.

Under-estimating beyond the margin the Revenue Code allows can lead to a surcharge. A new company without history should base its estimate on a documented business plan and keep a note of its reasoning.

Each deadline runs from the period end or half-year end as the Revenue Department announces, and e-filing may carry a different deadline from paper filing. Check the Revenue Department’s tax calendar every year.

The standard corporate income tax rate is set by the Revenue Code and related royal decrees. A small company that meets the paid-up capital and revenue tests may qualify for stepped rates, and a BOI-promoted company may receive an exemption or reduction under its promotion certificate.

These conditions can be checked with the Revenue Department and the Board of Investment. This page does not fix the rate figures, because rates and conditions change by announcement.

Expenses without a tax invoice or clear payment evidence, directors’ personal expenses, and service fees paid to a foreign parent without a contract and proof the service was actually delivered are the items reviewers look at most often.

Payments abroad such as royalties, service fees or interest usually trigger withholding tax, and may require the payer to remit VAT on behalf of the foreign supplier. Check the double tax agreement between Thailand and the recipient’s country before paying.

The Revenue Code lists expenses that cannot be deducted in computing net profit, such as personal expenses, expenses without a real recipient, expenses unrelated to the business, certain reserves, entertainment above the limit, and tax penalties and surcharges. Expenses shared between personal and company use, such as cars or housing, need clear policies and evidence.

Transactions with related companies or shareholders, such as loans, service fees or royalties, should have contracts and arm’s-length pricing, and companies meeting the criteria must file a related-party transaction disclosure as required by the Revenue Department.

PND 51 is the half-year return, based on estimated net profit or, under certain conditions, half-year statements. Tax paid is credited when filing PND 50, the year-end return based on audited statements. If profit is underestimated beyond the legal tolerance without reasonable cause, a surcharge may apply, so estimate carefully from real data.

A net tax loss can be carried forward against profits for the number of years the law allows, so keep the calculations throughout that period. Where tax withheld or paid at half-year exceeds the actual tax due, the company can claim a refund within the time limit, and the Revenue Department may review supporting documents before approving. Keep every original withholding tax certificate.

During the year: separate personal from company spending, keep every tax invoice and every withholding certificate issued to the company, and make sure related-company transactions have contracts and documents.

Before PND 51: estimate profit from actual first-half results and the second-half outlook, and record the reasoning behind the figures.

Before PND 50: convert accounting profit to taxable profit by checking non-deductible expenses, exempt income, any BOI incentives and losses brought forward, then reconcile tax withheld and half-year tax already paid.

Must a BOI-promoted company file? Yes, as usual, even with a tax exemption on the promoted activity, and it must separate income and expenses of promoted and non-promoted activities as the Board of Investment requires.

Can we file online? The Revenue Department offers online filing and payment after registration for the service. Keep proof of each filing and payment.

What if a return was wrong? An additional return can be filed to correct it under the rules. Correcting voluntarily before an inspection is generally better than leaving it.

If the Revenue Department issues a summons or invitation, read which periods and documents it covers, note the date, and prepare the documents listed, such as the general ledger, statements, returns, contracts and evidence of major expenses. If more time is needed, request a postponement in writing with reasons before the date. Whoever attends for the company should hold a power of attorney, ideally with the bookkeeper or auditor who knows the records. Answering with documented facts and recording everything handed over reduces later disputes.

Keep with PND 50 and PND 51 the audited statements, the book-to-tax reconciliation, withholding certificates issued to the company, proof of tax payment and any BOI certificates. This set helps answer officials quickly during a review.

This page gives general information drawn from the laws and notices of the agencies named, not advice on a specific case. Laws, rates and deadlines can change, so check with the Revenue Department, Department of Business Development or Social Security Office before deciding. Where the stakes are high, such as a tax audit, several years of overdue statements or cross-border transactions, have a licensed auditor or tax adviser review your actual documents.