Singapore GST Invoice Requirements: UEN & 9% GST Explained
Written by Naresh, Founder of QWIK INVOICE · Last updated: 26 August 2026
Short version: every Singapore business already has a UEN from ACRA, and that same number doubles as your GST registration number the moment you register. You must register for GST once your taxable turnover crosses S$1 million, after which every invoice needs a 9% GST line — the rate that took effect 1 January 2024. Below S$1,000, a shorter simplified tax invoice is enough; above it, IRAS expects the full set of fields.
What every Singapore invoice needs, GST or not
- Your business name and UEN — the identifier ACRA assigned when you registered, shown on every invoice regardless of GST status.
- Your business address and contact details.
- Your customer's name (address required only above S$1,000 — see below).
- A clear description of the goods or services supplied.
- The invoice date and a unique invoice number.
- The amount charged, and the total payable.
These fields apply whether or not you're GST-registered. Registration only changes what gets added on top, not the baseline every commercial invoice needs.
The UEN: one number, two jobs
Singapore doesn't issue a separate tax ID the way some countries do. Your UEN (Unique Entity Number) — assigned by ACRA when you incorporate a company, register a business, or set up most other entity types — is also the number IRAS uses as your GST registration number once you register, a practice in place since 2009. Practically, that means:
- Your UEN belongs on every invoice from day one, GST-registered or not — it's your business's legal identifier.
- Once GST-registered, you don't need to hunt down a separate GST number — quote the same UEN.
- Sole proprietors and partnerships registered with ACRA get a UEN too, not just companies.
GST registration — the S$1 million threshold
Registration is compulsory once your taxable turnover exceeds S$1 million, tested two ways:
- Retrospective view: your taxable turnover at the end of any calendar year exceeded S$1 million over the past 12 months.
- Prospective view: you can reasonably expect your taxable turnover to exceed S$1 million in the next 12 months, based on signed contracts or firm business activity.
You must register within 30 days of becoming liable under either test. Below the threshold, voluntary registration is available — useful if you want to claim GST credits on your own purchases — but IRAS requires voluntarily registered businesses to stay registered for at least 2 years, so it's worth planning around rather than opting in casually.
The GST rate — 9% since 1 January 2024
Singapore's GST rate rose in two scheduled steps: from 7% to 8% on 1 January 2023, then from 8% to 9% on 1 January 2024, where it currently stands. If you're reusing an old invoice template or a spreadsheet formula built before the increase, it's worth double-checking the rate is actually set to 9% and not a leftover 7% or 8%.
Full tax invoice vs simplified tax invoice
Like several GST/VAT systems, Singapore scales the required detail by transaction size — see IRAS's own guidance on invoicing customers for the full field-by-field breakdown:
| Sale amount (incl. GST) | Requirement |
|---|---|
| S$1,000 or less | A simplified tax invoice is acceptable — shorter field list, no customer name/address required |
| Above S$1,000 | A full tax invoice is required, including the customer's name and address |
Either way, a GST-registered business must issue an invoice within 30 days of the time of supply — the point at which the goods are delivered or the service is performed, or an earlier payment/ invoice date if that comes first.
What a full tax invoice needs beyond the basics
| Field | Detail |
|---|---|
| The words "Tax Invoice" | Stated clearly on the document |
| Seller's UEN / GST registration number | Required on every tax invoice |
| Customer's name and address | Required once the sale exceeds S$1,000 |
| Quantity and price per item | Shown excluding GST, per line item |
| GST rate and amount | 9%, shown as a separate amount — or a clear statement that the price includes GST |
| Total excluding GST, GST amount, and total including GST | All three shown, not just the final payable figure |
A simplified tax invoice (S$1,000 or less) only needs the seller's name, address and UEN, the invoice number and date, a description of what was sold, and the total amount payable with a statement that it includes GST — no separate GST breakdown or customer details required.
Worked example
| Business | GST status | What the invoice needs |
|---|---|---|
| Sole proprietor consultant, S$400,000/year turnover | Not GST-registered (below S$1 million) | Standard fields + UEN, no GST line, not called a "tax invoice" |
| Design studio Pte Ltd, S$1.5 million/year turnover | GST-registered (compulsory) | Full tax invoice: UEN, 9% GST breakdown, customer details on invoices above S$1,000 |
| Same studio, small S$300 retainer top-up | GST-registered | Simplified tax invoice is sufficient — UEN, total incl. GST, no customer address required |
QWIK INVOICE's international invoice generator covers this directly — the Standard (USA / Global) format includes a Tax ID field for your UEN and a single tax rate you can set to 9% (or leave blank if you're not registered), with SGD as a currency option. Add your business details once in Settings, and every invoice after that carries them automatically — open the generator to try it.
Frequently asked questions
What is a UEN, and do I need one to invoice in Singapore?
A UEN (Unique Entity Number) is the standard identification number ACRA issues to every business, company and organisation registered in Singapore. You need one to operate legally, and once you're GST-registered, IRAS uses that same UEN as your GST registration number — there's no separate tax ID to track.
When do I need to register for GST in Singapore?
Registration is compulsory once your taxable turnover exceeds S$1 million, either looking back over the past 12 months or forecast to exceed it in the next 12 months. You must register within 30 days of becoming liable. Below that threshold, you can register voluntarily, but IRAS requires you to stay registered for at least 2 years once you do.
What is the current GST rate in Singapore?
9%, effective from 1 January 2024. It rose in two steps from 7% — to 8% on 1 January 2023, then to 9% on 1 January 2024 — as part of a pre-announced increase, so double-check you're not still applying an old rate on a template carried over from before 2024.
Do I need a full tax invoice for every sale?
No. For a total of S$1,000 or less (including GST), IRAS allows a simplified tax invoice with a shorter field list. Above S$1,000, a full tax invoice is required, including the customer's name and address. Either way, GST-registered businesses must issue an invoice within 30 days of the time of supply.
Can I charge GST if I'm not registered?
No. Charging GST without being registered is not permitted — an unregistered business issues a plain invoice with no GST line and no reference to a 'tax invoice'. Only a GST-registered business, quoting its UEN as the GST registration number, can add GST to an invoice.
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