Invoicing & tax for a Architect in Thailand
A Architect in Thailand invoices clients with a receipt or tax invoice; when the client is a company, the client withholds 3% tax on the fee (income type: Professional fees), transfers you the net, and hands you a 50 Tawi (50 ทวิ) withholding certificate as proof. Example: on a ฿80,000.00 fee plus 7% VAT, the client withholds ฿2,400.00 and you actually receive ฿83,200.00. You keep the 50 Tawi to credit that tax on your annual return. On your own sales invoice you are the payee — the client withholds and issues the 50 Tawi, not you.
Architectural design and professional services are “professional fees” under Section 40(6), withheld at 3%; above ฿1.8M/year you must register for VAT and add 7%.
By the BillsOS team · Updated 9 Jun 2026
A worked example
Say you are a Architect invoicing a corporate client ฿80,000.00 for your work. The income type is “Professional fees”, withheld at 3%, and since you are VAT-registered you add 7% VAT. The figures below come straight from the BillsOS engine.
| Fee (before VAT) | ฿80,000.00 |
| VAT 7% | ฿5,600.00 |
| Total invoiced | ฿85,600.00 |
| Less withholding tax 3% | -฿2,400.00 |
| Net the client pays (QR amount) | ฿83,200.00 |
The client withholds ฿2,400.00 and transfers you ฿83,200.00, handing you a 50 Tawi certificate as evidence.
Who withholds: On your own sales invoice you are the payee. Your client (the payer) is the one who withholds the tax and issues you the 50 Tawi — you do not issue it yourself.
What to watch for in this trade
Architect fees sit under Section 40(6) professional income (distinct from ordinary hire-of-work even though both withhold 3%), so the 50 Tawi must tick the right income box.
Real-world scenarios
Scenario 1
An architect designs an office building for a large client across four payment phases in one year. The first phases together stay under ฿1.8M, but phase 3 pushes cumulative income over the threshold — so the architect registers for VAT and starts issuing 7% VAT tax invoices from phase 3 onward, while phases 1-2 remain plain receipts with no VAT.
Scenario 2
On the same project, the architect (working as an individual) hires an independent structural engineer for ฿60,000 worth of calculations, with no withholding between them since the architect isn't operating as a juristic person. Each reports their own share of the income separately on their personal returns.
The figures and details above are illustrative examples, not a Revenue Department ruling on your specific case.
Documents you’ll need
- Tax invoice / receipt — being VAT-registered, you issue a tax invoice with 7% VAT
- Quotation and invoice — before the work and when you bill
- 50 Tawi — received from the client and kept for every job, to credit on your annual return
Frequently asked questions for this trade
How is an architect’s professional fee different from hire-of-work on the 50 Tawi?+
A design project spans a year with phased payments — if my cumulative income crosses ฿1.8M mid-project, what happens?+
As an individual architect, I subcontract a structural engineer on the same project — do I have to withhold tax on their fee?+
Tools & guides for this
- Withholding tax & VAT calculator
- Free 50 Tawi generator
- Which documents a freelancer needs · Withholding tax rates · Freelancers & VAT
- Common Thai tax questions
Other freelance professions
- Invoicing & tax for a Graphic Designer
- Invoicing & tax for a Programmer
- Invoicing & tax for a Web Developer
BillsOS issues invoices and receipts that compute the withholding and 7% VAT for you, with an exact-amount PromptPay QR embedded so the client scans and pays straight into your own account.
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BillsOS only formats and computes documents for you. This is general information, not tax advice — please confirm with the Revenue Department or your accountant.