Is BillsOS’s tax invoice software compliant with the Revenue Department?

Yes — BillsOS produces tax invoices (full and abbreviated), receipts, and 50 Tawi in the Revenue Department format, laying out all the fields required under Sections 86/4 and 86/6. You still enter the name, address, and tax ID correctly yourself, and BillsOS does not file taxes or give tax advice on your behalf.

Can I use BillsOS if I am not yet VAT-registered?

Yes, but you cannot issue a tax invoice, because the law grants that right only to VAT-registered operators (Section 86). Turn the VAT switch off and issue receipts or quotations instead. Once you register for VAT (revenue over 1.8 million baht/year, or by choosing to register), turn VAT on to issue tax invoices.

How do full and abbreviated tax invoices differ, and which should I issue?

The full form (s.86/4) requires the buyer’s name and address and shows VAT separately — the customer can claim it as input VAT. The abbreviated form (s.86/6) may be issued only by retail / small-scale service businesses, does not require buyer details, and is VAT-inclusive. If your customer is a company or wants to claim a tax deduction, issue the full form.

Does the BillsOS PromptPay QR have fees, and where does the money go?

There is no per-bill fee from BillsOS — the PromptPay QR fills in the amount automatically and customers pay directly into your bank account. BillsOS never holds your funds. (Standard bank PromptPay fees may still apply.)

Can I also issue 50 Tawi withholding-tax certificates?

Yes — it is included from the Freelancer plan (฿390/month), ideal for freelancers whose corporate clients withhold tax at source and request the 50 Tawi document.

How do I get started, and is there a free option?

Yes — the free Starter plan lets you issue 5 bills/month. Sign up at /signup with no credit card. For higher volume and 50 Tawi, upgrade to Freelancer ฿390 or Pro ฿490 later.

Which documents does a freelancer need to bill a client and get paid?

A common sequence is quotation → invoice (with an exact-amount PromptPay QR) → once paid, a receipt, or a combined Tax Invoice / Receipt if you are VAT-registered. If a corporate client withholds tax, keep the 50 Tawi they give you. You can issue these as an individual, with no company. See the freelancer-documents guide for details.

What is the difference between a quotation, a billing note, and an invoice?

A quotation is issued before the job to propose a price for the client to approve. A billing note totals what is owed and sets a collection date (common with corporate clients). An invoice requests payment for delivered work before it is received. None of these three is itself a tax document — the tax documents are the receipt and the tax invoice.

Can I issue a tax invoice to a foreign client or in a foreign currency?

Yes — you can issue the document in a foreign currency, but a Thai tax invoice should also state the value in baht, converted under Revenue Department rules (generally based on the Bank of Thailand reference rate). BillsOS can show both currencies on one document. Some exported services may qualify for 0% VAT, but the conditions are detailed — have your accountant confirm first.

Online tax invoice software

Online tax invoice software — issue bills that are compliant with the Thai Revenue Department, free to start

A tax invoice (ใบกำกับภาษี) is a tax document under Thai Revenue Code Section 86, issued only by operators registered for VAT. The full form must show the issuer's name, address and tax ID; the buyer's details; item descriptions; and the VAT amount shown separately (Section 86/4), which lets the buyer claim input-VAT credit. To issue one you must first register for VAT, which is mandatory once annual revenue exceeds ฿1.8M. Document tools like BillsOS help you produce invoices in the Revenue Department's required format, with a PromptPay QR that fills in the exact amount and sends payment straight to your own bank account.

BillsOS is online tax invoice software for Thai freelancers and small shops. Issue full and abbreviated tax invoices, receipts, quotations, and 50 Tawi withholding-tax certificates in the format set by the Revenue Department, with a PromptPay QR that fills in the exact amount for you. Money lands directly in your account. Start free, no credit card.

By the BillsOS team · Updated 6 June 2026

This article provides general information for understanding only and is not specific tax or accounting advice. If unsure, consult a licensed accountant or the Revenue Department.

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What a legally compliant tax invoice must contain

Before choosing billing software, the most important thing is that the document it produces is complete under the Revenue Code. If fields are missing, your buyer may be unable to claim it as input VAT, and you yourself may have problems during a Revenue audit.

A full-form tax invoice, under Section 86/4 of the Revenue Code, must contain at least the following:

The words "Tax Invoice" (ใบกำกับภาษี) shown prominently
Name, address, and tax identification number of the registered operator issuing the invoice
Name and address of the buyer of goods or recipient of services
Sequential number of the invoice, and the book number (if any)
Name, kind, type, quantity, and value of the goods or services
The amount of VAT calculated on the value of goods or services, clearly separated from the value of the goods
The day, month, and year the invoice is issued
Other particulars prescribed by the Director-General of the Revenue Department (e.g. "documents issued as a set" in certain cases)

Note: a full-form tax invoice must clearly state whether the displayed price includes or excludes VAT, and must show the VAT amount separately.

BillsOS lays out all eight of these fields in a single form and calculates 7% VAT on a separate line automatically. You just enter the name, address, and tax ID correctly — the system arranges the rest.

Full-form vs abbreviated tax invoice

Item	Full form (s.86/4)	Abbreviated (s.86/6)
Who may issue	Any VAT-registered operator	Only retail / small-scale service operators selling to many individuals, who are VAT-registered
Buyer details required	Yes — buyer name and address required	No — buyer name and address not required
Price / VAT display	VAT shown separately from price	Price is VAT-inclusive, with a clear statement to that effect
Buyer can claim input VAT	Yes	Generally cannot be used to claim input VAT credit (except in certain cases prescribed by law)

In short: if your customer is a company, or anyone who needs to claim input VAT, always issue the full form. The abbreviated form suits walk-in retail shops selling to many ordinary consumers — and the law grants this right only to retail businesses. BillsOS supports both and switches between them in a few clicks.

Tax invoice ≠ receipt ≠ invoice

Many people confuse these three documents:

Tax invoice — a tax document under the Revenue Code that shows the VAT amount; only VAT-registered operators may issue it.
Receipt — proof that payment has been received; can be issued even without VAT registration (non-VAT businesses often issue a "cash bill").
Invoice / billing note — a document requesting payment before it is received; not itself a tax document.

In practice many shops issue a combined "Tax Invoice / Receipt" on a single document when receiving cash — a format BillsOS supports.

You must register for VAT before you can issue a tax invoice

This is important and often missed: only operators registered for VAT may issue tax invoices. Under Section 86 of the Revenue Code, a registered operator is required to issue a tax invoice every time they sell goods or provide services.

Operators with revenue exceeding 1.8 million baht per year are required to register for VAT (filing form Phor.Phor.01 within 30 days of the date revenue exceeds the threshold).
Those not yet registered for VAT (below the threshold, or simply not registered) cannot issue tax invoices — issuing one without the right to do so carries legal penalties.
If not VAT-registered, issue a receipt / cash bill instead, which the buyer can still use as evidence of an expense (subject to Revenue Department conditions).

BillsOS has a VAT on/off switch: if you are not yet VAT-registered, leave it off and issue receipts or quotations. Once you register, turn it on to issue full or abbreviated tax invoices — no need to change software.

BillsOS is a document-creation tool — it does not file taxes for you and is not a tax adviser. If you are unsure whether you must register for VAT, consult an accountant or the Revenue Department.

What BillsOS does for you

Issue full and abbreviated tax invoices in the Revenue Department format, with all fields under s.86/4 / s.86/6.
Receipts, quotations, and 50 Tawi (withholding-tax certificates) in one app.
VAT on/off — works for both VAT-registered and non-registered businesses.
PromptPay QR with the exact amount filled in — customers scan and pay the precise total, and money lands directly in your bank account. BillsOS never holds your funds and charges no per-bill fee.
Bilingual Thai/English, suited to international clients.
Share via LINE — send a bill to your customer instantly.
CSV export (Pro plan) so your accountant can post the entries easily.

Who it is for

Freelancers whose corporate clients ask for tax invoices and withholding tax — 50 Tawi is available from the Freelancer plan.
Online shops / small shops that want exact-amount PromptPay and to send bills via LINE.
Businesses that have just registered for VAT and need to start issuing compliant tax invoices.
People not yet VAT-registered who simply want professional receipts and quotations.

BillsOS compared with FlowAccount and PEAK

Prices as of June 2026 — check the latest on each provider’s own page. All figures are the "entry plan that includes tax-invoice features".

Item	BillsOS	FlowAccount	PEAK
Entry price (with tax invoice)	฿390/mo (Freelancer) · free tier 5 bills/mo	฿165/mo (Standard, billed yearly ฿1,990)	e-Document ฿2,500/yr (≈฿208/mo)
Built-in PromptPay QR	Yes — amount auto-filled, paid straight to your account	Yes (Static; Dynamic via KBank)	Yes (plan-dependent)
Per-bill fee (PromptPay)	None — paid straight to your bank	—	—
50 Tawi (withholding)	Included from Freelancer ฿390	Yes (plan-dependent)	Yes (e-Document and up)
Full / abbreviated tax invoice	Both	Both	Both
Bilingual Thai/English	Yes	Yes	Yes
Strengths	Free start, no card; native PromptPay; transparent pricing	Full accounting system	Deep accounting, financial statements, for SMEs with accountants

Where BillsOS wins: it is built with PromptPay at its heart (amount filled in, money straight to your account, no per-bill fee), it is the simplest option for anyone who just wants to issue compliant bills and get paid, 50 Tawi is included in the entry plan, and pricing is transparent with a free tier you can try without a card.

Where competitors fit better (frankly): if you need a full accounting system — general ledger, financial statements, multi-channel e-commerce integration, or a team of several accountants — FlowAccount and PEAK have more complete modules. BillsOS focuses on billing plus getting paid, as fast as possible.

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How to get started (3 steps)

Sign up free at /signup — no credit card.
Enter your business details (name, address, tax ID) and turn VAT on/off to match your status.
Issue a tax invoice + PromptPay QR, send it to your customer via LINE, and receive money straight to your account.

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Quotation, billing note, invoice, receipt, tax invoice — which to issue, and when

The question Thai freelancers and small shops ask most is “which documents do I issue to bill a client?” Each document has a different job and is issued at a different point in the job. BillsOS produces all of them in one place, and every one can carry a PromptPay QR with the amount filled in for you.

Document	When you issue it	A tax document?
Quotation	Before the job — to propose a price for the client to approve	No
Billing note	To total what is owed and set a collection date (common with corporate clients)	No
Invoice	To request payment for delivered work/goods, before payment is received	No
Receipt	When you have received the money — proof of payment; can be issued even without VAT registration	Expense evidence
Tax invoice	When the VAT tax point arises — only VAT-registered operators may issue it	Yes (s.86/4 / 86/6)

A common freelancer sequence: quotation → (client agrees) → invoice with a PromptPay QR → client transfers → issue a receipt, or a combined Tax Invoice / Receipt if you are VAT-registered. If the client is a company that withholds tax, keep the 50 Tawi they issue you on file too.

You do not need a registered company or accounting software to issue these — you can issue them as an individual. Start free with 5 bills/month, no card.

Invoicing international clients and foreign currency from Thailand

Many freelancers and agencies in Thailand have clients abroad and bill in dollars or euros. The question is how to document this correctly and still get paid conveniently.

The document — you can issue an invoice or receipt in a foreign currency, but a Thai tax invoice should also state the value in baht. BillsOS can show both currencies on one document (e.g. USD with the THB equivalent).
Exchange rate — converting to baht must follow Revenue Department rules (generally based on the Bank of Thailand reference rate). Ask your accountant which day’s rate to use.
VAT — exported services consumed abroad can in some cases be zero-rated (0%), but the conditions are detailed and audited in practice. Have your accountant confirm before assuming every foreign job is 0%.
Getting paid — if your overseas client transfers to a Thai account linked to PromptPay, you can attach the exact-amount PromptPay QR as usual. Cross-border payment itself goes through your bank and is separate from the document.

Whether a foreigner owes tax in Thailand depends on each person’s tax residency and source of income — this is case-specific, so consult an accountant or the Revenue Department (hotline 1161). BillsOS is a document tool and does not give tax advice on your behalf.

แหล่งอ้างอิง / Sources

Primary sources from the Thai Revenue Department (rd.go.th) and secondary sources (provider pages and accounting guides). Competitor prices surveyed as of June 2026 and may change.

Primary — Revenue Department: Sections 85/86 Revenue Code (s.86, 86/4, 86/6)
Primary — Revenue Department: Tax invoice handbook (PDF)
Primary — Revenue Department: VAT Notice No. 39 (s.86/4(8))
Primary — Revenue Department: SME tax handbook (1.8M VAT threshold, PDF)
Secondary — provider page: FlowAccount — pricing page (surveyed June 2026)
Secondary — provider page: PEAK Account — package pricing (surveyed June 2026)
Secondary — accounting guide: iTAX — receipt vs tax invoice
Secondary — accounting guide: BeeAccountant — abbreviated tax invoice
Secondary — accounting guide: PEAK — revenue over 1.8M but not VAT-registered