Personal income tax

Thai tax deductions you can claim

Updated 5 September 2026

Most people overpay Thai income tax not because they do not know the allowances exist, but because the paperwork is scattered by the time they file. The insurance certificate is in an email from eight months ago, the donation receipts are gone, and nobody asked the bank for the mortgage interest letter.

This covers how the calculation is structured, which allowances are worth tracking, and what evidence each one needs.

How the calculation works

Thai personal income tax is not charged on gross income. It runs in stages: total assessable income for the year, minus a standard expense deduction that depends on the income type (salary is 50% capped at 100,000 baht), minus your allowances. What is left is net income, and that is what the progressive rate bands apply to.

The expense deduction is applied for you. The allowances are the layer you claim yourself, and the layer you need records for if you are ever asked.

Personal and family allowances

Allowance	Commonly	Evidence
Yourself	60,000 baht	None, applied automatically
Spouse with no income	60,000 baht	Marriage certificate
Each child	30,000 baht	Birth certificate or house registration
Each parent aged 60+	30,000 baht	Signed parent allowance form (Lor Yor 03)
Social security	As contributed	Employer or SSO statement

Life and health insurance

Life insurance premiums on your own policy are deductible as paid, commonly capped at 100,000 baht, and the policy generally has to run 10 years or longer.
Your own health insurance premiums are deductible too, but usually share that same ceiling once combined with life cover.
Health insurance premiums for your parents sit under a separate limit, and unlike the parent allowance they do not require the parent to be 60.

The evidence is the annual premium certificate the insurer issues, normally emailed early in the year. Monthly receipts are not what the Revenue Department wants.

Funds that still qualify, and one that does not

This is the area that changes most often, and where stale articles do the most damage.

RMF still qualifies. The limit is a percentage of assessable income and it counts inside the combined retirement ceiling, shared with provident funds and annuity premiums.
SSF closed to new purchases for deduction purposes on 1 January 2025. Units bought before then continue under their original conditions, but new money buys no deduction. Plenty of published guidance has not caught up.
Thai ESG took over that role. It carries its own separate limit that does not count against the retirement ceiling, with holding-period rules of its own.

Mortgage interest and donations

Interest on a loan to buy or build a home is deductible as paid, commonly capped at 100,000 baht a year. Banks issue an annual interest certificate, and several Thai banks will not send it unless you request it in the app.

Donations are deductible up to a proportion of income after expenses and other allowances. Gifts to schools, state hospitals and certain bodies are deductible at double value. Keep the receipt, or make the donation through e-Donation so it is recorded electronically.

What changed for tax year 2569

One number moved, and it is the one most published guidance has not updated. The social security contribution ceiling rose from 15,000 to 17,500 baht a month on 1 January 2026. The rate stayed at 5%, so the monthly maximum went from 750 to 875 baht and the most you can deduct for the year went from 9,000 to 10,500.

It is a small figure on its own. It matters because a calculator or article still showing 9,000 for tax year 2569 is working from last year's rules, and whatever else it says about the caps deserves the same suspicion.

A worked example

Take a salary of 600,000 baht for the year, 50,000 a month, with social security deducted and nothing else claimed.

Step	Amount
Assessable income	600,000
Less expense deduction (50%, capped)	-100,000
Less personal allowance	-60,000
Less social security	-10,500
Net income taxed	429,500
Tax for the year	20,450

The 429,500 is not taxed at one rate. The first 150,000 is exempt, the next 150,000 is taxed at 5% (7,500 baht), and the remaining 129,500 at 10% (12,950 baht). That is where the 20,450 comes from.

Now put 100,000 baht into RMF and pay a 30,000 baht life premium. Deductions rise to 200,500, net income falls to 299,500, and the tax falls to 7,475. So 130,000 baht of claims saved 12,975.

What to keep during the year

Filing gets much easier if these are collected as they arrive rather than hunted down in March.

Withholding tax certificates (50 Tawi) from every employer and client
Annual premium certificates for every life and health policy
The bank's annual mortgage interest certificate
Fund purchase confirmations from the asset management company
Donation receipts, or e-Donation records
Bank statements showing the payments actually left your account, in case anything is queried

Common mistakes

Two siblings both claiming the same parent. Only one of you can, and the Revenue Department will find the duplicate.
Filing monthly insurance receipts instead of the annual premium certificate. The certificate is the document that counts.
Assuming SSF still reduces this year's tax. It does not, for any purchase made from 1 January 2025.
Never asking the bank for the mortgage interest certificate. Several Thai banks issue it only on request in the app.
Donating in cash with no receipt. e-Donation records it for you and removes the paperwork question entirely.
Leaving all of it until March. Every item above is easier to obtain during the year than after it has ended.

Deadlines

Paper returns are due by the end of March following the tax year. Filing online through the Revenue Department usually extends that into early April. If you owe additional tax above a threshold, you can apply to pay in instalments.