Filing Thai Personal Income Tax Online: A Beginner’s Guide
Your first return is easier than it looks — once you know which form you need, which papers to gather, and what to check before you confirm.
Who has to file, and why it matters
Personal income tax is worked out from what you received across the calendar year, less the expenses and allowances the law grants, with tax charged on what remains. It is not a salaried person’s concern alone: it reaches freelancers, online sellers, landlords and anyone drawing interest or dividends. Monthly withholding is only an advance estimate — the annual return is where the real arithmetic happens.
PND 91 and PND 90, side by side
This is where beginners get stuck most often, and a leading reason people end up filing twice. The test is simple: did your money for the year arrive through one door, or several?
| Form | Use it when | Typical filer |
|---|---|---|
| PND 91 | Employment was your only income all tax year | A salaried employee with no side work, rent or dividends |
| PND 90 | You had other categories of income, with or without a salary | A freelancer, online seller, landlord, or an employee taking outside work |
What to have in front of you
- A 50 ทวิ certificate from every employer and payer you had that year
- Life and health insurance premium statements, yours and your parents’
- Provident fund reports and certificates for qualifying retirement funds
- Your bank’s certificate of interest paid on a home loan
- Donation receipts, including anything logged in the electronic donation system
- National ID numbers for the spouse, children and parents you intend to claim
The families of allowance
| Group | What it covers |
|---|---|
| Personal and family | Yourself, a spouse without income, children, parents, dependants with a disability |
| Insurance and health | Life premiums, health cover for you and your parents, pension-type life policies |
| Retirement saving | Provident funds, the civil servant pension fund, the national savings fund, retirement funds |
| Housing | Interest on a loan to buy, hire-purchase or build a home |
| Donations | General giving, plus categories the law treats more generously |
| Occasional measures | Deductions for spending or domestic travel announced year by year, and not every year |
When something goes wrong
- Pre-filled income does not match your 50 ทวิ: trust the document, and ask HR or the payer to check what they submitted. Do not confirm while the gap is unexplained — fixing it beforehand is always easier.
- A missing 50 ทวิ from a former employer: the payer is legally required to issue one, so request it in writing and name the tax year. Keep your payslips meanwhile, and if the company is truly unreachable, take what evidence you have to an area revenue office.
- You missed the deadline: you must still file, and the sooner the better, because late filing carries surcharges and penalties set by law. Check with the Revenue Department whether that year can still go through the online channel or must be lodged at an area office.
Refund scams to watch for
Filing season is peak season for fraud, precisely because so many people really are waiting on a refund. The usual approach is an SMS or email saying your refund is pending confirmation, with a link asking for your ID number, bank account or an OTP. Some build a lookalike page on a domain spelled just closely enough to slip past a quick glance.
- Refunds reach the account you linked yourself, or PromptPay tied to your national ID. No genuine step asks for a card security number or an OTP.
- Do not tap links in messages. Type the Revenue Department’s address yourself, or use a bookmark you saved.
- Read the domain carefully before typing anything: the official systems sit under rd.go.th and nowhere else.
- No official asks you to transfer a processing fee to release a refund. If someone does, end the call and check through an official channel yourself.
How to use it
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Check whether you have to file
If your income reaches the threshold set in law you must file, even when nothing turns out to be payable. The threshold differs by income type and marital status, so check your tax year’s figure on the Revenue Department’s site. And where tax was withheld from you during the year, filing is the only way to get the excess back.
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Get the form right from the start
Salary alone all year means PND 91. The moment anything else appears — freelance fees, rent, dividends — you need PND 90 instead. Choose wrong and the fields you need are simply not there, which usually ends in filing all over again.
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Gather the paperwork before you start
The centrepiece is the withholding tax certificate — the หนังสือรับรองการหักภาษี ณ ที่จ่าย everyone calls a 50 ทวิ — and you need one from every employer you had that year, not just your current one. Then collect the deduction side in full. Having it all to hand is what lets you finish in one sitting.
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Register and verify your identity
First-time online filers register with a national ID number and details that match the civil registration record. Use a phone number and email you can genuinely reach, because verification codes and status notices arrive there. If you have filed before and forgotten your password, you can reset it yourself.
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Check the pre-filled income
The system may pre-fill your income and withheld tax from what employers reported. Treat it as a head start, not a verdict: compare every 50 ทวิ against it, payer by payer. Some report late or incompletely, and you may have income from a payer that never appears there at all.
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Enter allowances you can document
Claim only what you can evidence, using the amount printed on the document rather than the one you half-remember. Unsure how far a right extends? Check that tax year’s conditions on the Revenue Department site. Keep the whole bundle afterwards, in case an officer asks to see it.
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Read the result, then refund or pay
The system shows whether you owe a balance or are due a refund. If it is far from what you expected, revisit the income and allowance fields first — a stray digit or a figure entered twice explains most surprises. Save the confirmation once you submit, and for a refund link a bank account in your own name or PromptPay registered to your national ID.
Frequently asked questions
My income is low. Do I still need to file?
The duty to file and the duty to pay are separate. If your income reaches the statutory threshold you must file, even when the calculation leaves nothing payable. The threshold is revised periodically, so check the figure for your tax year on the Revenue Department site.
My employer withholds tax monthly. Why file again?
Withholding is calculated from what your employer knew at the start of the year. It cannot account for what happened afterwards — a new policy, a child, a mortgage, a change of job midway. The annual return recalculates from the real year, which is why it can end in a refund or a balance due.
I have a salary and freelance work. Which form?
PND 90, because you have more than one category of income. Salary goes in the employment section; freelance fees go under the category matching the nature of the work. If you are unsure which category your earnings fall into, ask an area revenue office before submitting.
How does a refund reach me, and can I track it?
The smoothest route is PromptPay registered to your own national ID, or a bank account in your name; the money transfers straight there. You can follow the refund’s status yourself inside the system. Officers sometimes request supporting documents before approving, and they ask through official channels — never a link by SMS.
Is ThaiGov.co connected to the Revenue Department?
No. ThaiGov.co is an independently produced directory of Thai government online services, not affiliated with or appointed by any agency. This page explains the process in plain language and then sends you to the official system to do the actual work. We never collect tax data, documents or payments.