How to File a Tax Return in Thailand: PND 90 and PND 91.

Who has to file a Thai tax return

Everyone who earns above a low threshold in Thailand has to file a tax return, whether or not any tax turns out to be due. Two forms carry almost every personal filing: PND 90 and PND 91. What follows is how to file a tax return in Thailand, which form applies, when it is due, how the tax is paid, and what late filing costs.

The Revenue Department is blunt about the trigger. Its page on the minimum income for filing states that the duty arises once assessable income reaches the legal minimum, whether or not the calculation ends in tax to pay. Assessable income is the term for income the Revenue Code brings into charge, in cash or in kind.

Those figures sit well below the point where tax actually starts, which is why so many salaried residents file a return and pay nothing.

Residency changes what goes on the return rather than whether one is filed. A person in Thailand for more than 180 days in a calendar year is a resident for tax, charged on Thai income plus foreign income brought into Thailand, while a non-resident is charged on Thai-source income only, as the Revenue Department's English overview of personal income tax puts it. The full residency and foreign-income picture is in Thailand tax residency and income tax for foreigners. The residency count, the eight income categories, the deductions and the rate bands are covered under personal income tax in Thailand.

A company's own returns run on a separate calendar with separate forms, set out in the Thai company compliance calendar.

PND 90, PND 91 and the other personal tax forms

The form is chosen by the income mix rather than by who is filing. The Revenue Department's filing deadline page lists five personal returns.

Salary and nothing else is PND 91. One freelance invoice, one tenant or one dividend, and the return becomes PND 90.

PND 94 is the one that catches people out. Rent, professional fees, contracting income and business income, which are categories 5 to 8, trigger a half-year return when received between January and June, filed within September of that same year. The tax paid then is credited against the year-end bill, so it moves money forward rather than adding to it.

Employers can file PND 91 for their staff, but only in bulk. Regional Revenue Office 1 sets the floor at 50 employee records in the upload file and tells smaller employers to have staff file individually. The employer's own withholding duties are separate, and are covered in hiring employees in Thailand.

Thai tax filing deadlines, and the eight extra days for online filing

The statute is short. The year-end return is filed and the tax paid within the last day of March following the tax year, and the half-year return within the last day of September of that tax year.

The eight extra days for internet filing sit on top of that as a separate grant. The Minister of Finance uses Section 3 Octo paragraph 2 of the Revenue Code to extend internet filing, payment and remittance by eight days beyond the legal deadline, for a defined period at a time, as the Revenue Department's clarification on the internet filing extension records. It has been renewed repeatedly since 2012, and every grant carries an end date, so the online date is checked each year rather than assumed.

Dates for the tax year 2025 cycle, filed during 2026:

The 8 April 2026 cutoff appears in writing on Regional Revenue Office 1's tax year 2025 employer filing notice, which ran the filing service and the RD Payroll 90/91 download from 17 February 2026 to 8 April 2026. For any later cycle, the Revenue Department's month by month tax calendar prints the statutory date and the internet date side by side.

How to file a tax return in Thailand, step by step

1. Collect the paperwork. Withholding tax certificates from every payer, receipts for anything being claimed, and the bank details for a refund.
2. Confirm the taxpayer identification number. Registering for one is a listed duty of every taxpayer on the Revenue Department's rights and duties of a taxpayer page.
3. Pick the form from the table above.
4. File it, online or on paper at the district Revenue office covering the address on the return.
5. Pay, if the calculation ends in tax due, by the filing deadline.
6. Keep the proof. Online filing returns a reference number, and where no tax is due the receipt follows immediately. On paper, the officer's receipt doubles as proof of filing.

Filing online versus filing on paper

The e-filing service handles PND 90, 91, 94 and 95, original and amended returns, inside and outside the deadline. A registered tax agent, meaning an accounting office authorised to file for its clients, can file on a taxpayer's behalf. A provider that only prepares form data through the Open API does not file it, and the taxpayer still files through the RD Smart Tax app.

That last row is the expensive one. The Revenue Department's warning on late PND 90 and 91 filing states that where a return goes in over the internet with tax to pay and the tax is not paid by 31 March, the return counts as never filed, and has to be filed again at a branch office with the surcharge and the fine on top. That page is written against the statutory March date.

Identity is where a foreign filer meets friction. Registering as an individual on the e-filing registration page covers PND 90, 91, 94 and 95 and issues a username and password for immediate use, with Digital ID through ThaID, the Paotang app or a bank NDID login as an alternative. The plumbing underneath still assumes a Thai national ID in places: signing into the D-MyTax portal with an RD ID asks for the laser code on the back of a Thai identity card, and a PromptPay refund works only where PromptPay is registered against a 13-digit Thai national ID. No official page states that a foreign national cannot register for e-filing, and the department's own document rules expect a certified passport copy from a filer with no Thai identity card. A filer in that position files under a number issued on application, and tax identification number in Thailand explains how to get one.

What filing actually costs

Filing itself is free, and the costs attached to it are small and specific.

Paying by electronic card is accepted only at the branch offices listed on the payment methods page, which are in Bangkok and eight nearby provinces, and the card fee falls on the cardholder. Cheques cannot be post-dated or endorsed over from a third party, cannot exceed the tax due, and count as payment only once the Revenue Department has the money.

Professional help is the real variable, and there is no official figure for it. The Revenue Department publishes no fee schedule for tax advisers and no survey of market rates, so any figure quoted online is a private price rather than a published one. A firm listed among tax consultants in Thailand will quote for the specific return.

Paying the tax, and the three-installment option

Personal income tax of 3,000 baht or more, half-year or year-end, can be paid in three equal installments with no surcharge. The Revenue Department's page on paying by installment puts the request at a district Revenue office on form Bor Chor 35, with the first installment due with the return and each of the next two a month after the one before. That right comes with one hard condition: miss any installment and the right is lost, the whole outstanding balance falls due, and the surcharge of 1.5 percent per month runs on what is left.

Online filers pay by e-payment, through their bank's own electronic channels, or at a post office under Pay at Post. The receipt follows by registered post.

Fixing a mistake: amended returns and refunds

An amended return filed after the deadline is treated more gently than a late original. Where extra tax is due, the tax and the surcharge of 1.5 percent per month are payable but no fine is charged. Where the amendment produces no extra tax, neither applies.

Refunds run on three rails. A Thai national who has registered PromptPay against their 13-digit national ID is paid into that bank account. A claimant who does not want the PromptPay transfer is issued a Kor 21 refund notice to present at a Krungthai Bank or Bank for Agriculture and Agricultural Cooperatives branch. A claimant who cannot register PromptPay against a 13-digit national ID receives the Kor 21 with a cheque, posted to the address on the return and depositable only at a bank branch. The Revenue Department's refund information page names foreign nationals, non-juristic ordinary partnerships, bodies of persons, community enterprises and undivided estates in that last group.

Where the return did not ask for a refund and tax was overpaid anyway, the claim goes on form Kor 10 at the area Revenue office for the filer's domicile, within three years of the last day of the filing deadline, with withholding certificates and supporting receipts attached.

Timing is published, which is unusual. Where the documents clearly show tax overpaid, paid in error, paid twice or not payable at all, the Revenue Department states that it refunds within three months of receiving the request. Status is tracked in the D-MyTax portal, and supporting documents go in by hand, by fax, by post, or by upload in JPG, BMP, PNG, TIF or PDF, up to 10 MB a file and 50 MB a batch, with password-protected PDFs rejected.

A refund that is refused or paid short is challenged in writing to the officer who made the decision, within 15 days of the notice. What that route involves in practice sits under tax refund claims in Thailand.

What late filing costs: fine, surcharge and criminal exposure

The consequences form a ladder, and most filers never leave the bottom rung. The Revenue Department's page on paying late sets out the upper ones.

Two things sit behind that table, both from the same rights and duties page. A tax officer has no power to waive or reduce the surcharge, and it drops to half only where the Director-General grants an extension of time and the tax is paid inside it. And a taxpayer who disagrees with an assessment appeals to the Commission of Appeals on form P.S.6 within 30 days of the notice, with a further 30 days to challenge the ruling, after which the right lapses and the full amount stands. Appealing does not postpone payment, which is why security is lodged instead. Tax dispute lawyers in Thailand handle that stage.

Foreign income, LTR visa holders and leaving Thailand

Foreign income is the live question for resident foreigners. A resident is charged on the portion of foreign income brought into Thailand, and remittances have been assessed on that basis since the start of 2024. The Bangkok Post ran a December 2025 discussion of how unsettled the detail still is: what counts as a remittance, how savings held before 2024 are treated, and how double tax agreements interact. A tax adviser can check what applies to a given year before the return goes in.

Long-term resident visa holders sit under their own rules. The Board of Investment's LTR laws and regulations page lists Royal Decree No. 743 issued under the Revenue Code and Notification of Income Tax No. 427 among the instruments behind the visa, which is where that tax treatment lives. The visa is set beside the alternatives in Thailand's long-term visa options.

Leaving Thailand raises the tax clearance certificate, which worries more people than it affects. Section 4 quarter of the Revenue Code requires a departing foreigner to apply within 15 days before leaving, but the Revenue Department's tax clearance certificate page narrows that to three cases: tax or arrears are payable, the person files on behalf of a foreign company carrying on business in Thailand, or the income comes from performing publicly in Thailand. A Director-General notification of 7 May 1991 confirms that departing foreigners outside those three cases do not have to apply, and the section itself excludes transit passengers and foreigners in Thailand for 90 days or less in a tax year without assessable income. Where a certificate is needed, form P.3 covers a single departure and is valid for 15 days, and P.3.1 covers regular travel for up to 180 days. Departing without one where it was required attracts a surcharge of 20 percent of the tax, plus a fine of up to 1,000 baht or up to one month in prison, or both.

When a tax adviser is worth it

Most salaried filers with one employer and no side income can complete PND 91 unaided. Paid help earns its fee somewhere else: income landing in several categories at once, a first year of Thai residency, foreign income with a treaty question attached, a property sale where withholding was taken at the Land Department, a refund that has stalled, or an assessment letter. The withholding side of a sale is explained in property transfer fees in Thailand.

Company owners carry a second problem, keeping the personal return consistent with the books the company files. Thailand's accounting requirements cover that side. For the return itself, a tax lawyer in Thailand or a licensed accountant can check the treatment before it is filed, which costs less than arguing it afterwards.