Who needs a Tax ID in Thailand, how to register with Revenue Department, what the number looks like, how to find or check one, and where it goes on your invoices.
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Updated for 2026
Last reviewed September 2026
This is the general edition of this guide for Thailand. It explains how the Tax ID, VAT and annual filing work and names Revenue Department as the place to confirm thresholds and dates. Country-specific figures are added as each edition is reviewed.
What the Tax ID is
The Tax ID is the number Revenue Department assigns to a taxpayer in Thailand. It follows you across every tax you deal with: VAT, income tax and withholding. Businesses that pay you will ask for it before they release payment, because they report their suppliers to Revenue Department by this number.
Who needs one
Anyone who earns taxable income, runs a business, employs staff or wants to be paid by a company that must report its suppliers. In practice, if you invoice, you need one.
How to register, step by step
Gather your identity document and, for a business, the registration certificate and the owners' or directors' details.
Register with Revenue Department. Choose the taxes you will be liable for; do not add VAT unless you must or want to register for it.
Download or collect the registration certificate. It shows your Tax ID; keep the PDF, because clients will ask for it.
Add the Tax ID to your invoice template and letterhead.
How to find or check a Tax ID
Your own number is on the registration certificate and on every letter or notice from Revenue Department. Most authorities now offer an online lookup to confirm a supplier's number and registered name before you pay them; use it for any new supplier.
Where it goes on your paperwork
In the invoice header next to your business name, and in the client block when the client is a registered business. Quotations and purchase orders carry it too, so the client's accounts team can match documents. The Thailand invoice generator has a Tax ID field in both blocks.
Questions people ask
Does it cost anything to get a Tax ID?
Registration with Revenue Department is normally free. Agents charge for filling in the same form; pay one only if you want the time saved.
Can I invoice without a Tax ID?
You can write the document, but many clients will not pay an invoice that has no Tax ID, and you cannot charge VAT without being registered. Register first; it is usually quick.
Is the Tax ID the same as VAT registration?
Not necessarily. The Tax ID identifies you as a taxpayer; VAT registration is a separate status you take on when turnover passes the threshold or you opt in. Some countries use one number for both, others issue a separate VAT number.
How long does registration take?
Online registrations are often instant or take a few days; applications that need a visit or document checks take longer. Start before you need to send your first invoice.
Sources
Revenue Department — the official guidance for Thailand
How this guide was made
Written from published tax-authority guidance and reviewed on 2026-09-03. Everything here is indicative rather than a ruling on your circumstances, and rules change. Confirm anything you rely on with Revenue Department before acting on it, and tell us if you find something out of date so we can correct it.
This guide explains the rules in general terms and is not tax advice for your circumstances. Confirm your position with a qualified adviser or with Revenue Department.
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Tools for Thailand
Invoices, quotations, purchase orders, credit notes and waybills in THB, with VAT and the Tax ID on the document. Plus a VAT calculator. Everything runs in your browser and nothing is uploaded.