About BillsOS
BillsOS is a Thai invoicing and tax-compliance web app operated by Cavastir, built for freelancers and micro-businesses in Thailand. It issues tax invoices, receipts, quotations, and Section 50 Bis withholding-tax certificates (50 ทวิ) in the Revenue Department format, and generates PromptPay QR codes pre-filled with the exact amount — your client scans and pays straight into your own bank account. BillsOS never holds funds and charges no per-bill fee, and works in both Thai and English. BillsOS formats and computes documents only; it does not file returns for you and is not tax advice.
What does BillsOS do?
- Generates exact-amount PromptPay QR codes paid straight to your bank account
- Issues tax invoices and receipts in the Revenue Department format
- Creates 50 Bis withholding-tax certificates and computes VAT / withholding for you
- Quotations, and bilingual Thai/English documents
What does BillsOS NOT do?
- It is not a payment processor or e-wallet — it does not hold or move your money
- It is not a full accounting suite, and it does not file tax returns for you
- It does not provide tax advice — it only formats and computes documents
Who is behind BillsOS?
BillsOS is operated by the Cavastir team. We build our guides and tools from the Thai Revenue Department’s published rules and keep them current. The information on this site is general information to make Thai tax easier to understand — it is not individual tax advice. Please confirm with the Revenue Department or your accountant before acting.
How to contact us
Email: support@billsos.com · Contact page