How to invoice in Singapore: what a compliant invoice must show
The fields a Singapore invoice needs, how to number and date it, when to show GST, the e-invoicing rules, and how to fix a mistake with a credit note.
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Updated for 2026
Last reviewed September 2026
What every invoice must show
Whatever your trade, these fields are the minimum:
The word Invoice (or Tax Invoice where you charge GST) and a unique sequential number.
Issue date and, for services, the date or period of supply.
Your business name, address and UEN; your registration number if you have one.
The client's name and address, and their UEN when they are a registered business.
One line per item or service: description, quantity, unit price and line total in SGD.
Subtotal, GST rate and amount (or a statement that none was charged), and the total due.
Payment terms, due date and bank details.
In Singapore specifically:
A tax invoice with the words Tax Invoice, the GST registration number and the GST amount at 9%; simplified invoices under S$1,000.
Numbering and dates
Numbers must run in sequence with no gaps or repeats; Inland Revenue Authority of Singapore (IRAS) checks for both. Use a prefix per year or series if it helps (2026-001), but never reissue a number. The issue date fixes the tax period the sale falls into, so date the invoice when you send it, not when the work started.
Showing GST
Only registered businesses charge GST. If you are registered, show the rate and the amount as separate lines; if you are not, do not show a GST line and say so on the document. Charging GST without registration is an offence in most countries, and clients' accountants will spot it.
Electronic invoicing in Singapore
InvoiceNow (Peppol) phases in by size: new voluntary registrants from 1 November 2025 and 1 April 2026, then existing businesses by annual supplies, from 1 April 2028 for the smallest through 1 April 2031 for those above S$4 million. Confirm your wave with IRAS.
Many countries now require invoices to be issued through, or reported to, an official electronic system. Where Singapore does, the PDF you make here is a working document for quotes, proformas and internal records, and the fiscal invoice comes from the official system. Where it does not, an emailed PDF is a valid invoice.
Getting paid
State the due date, not just the terms. Put the bank details on the invoice and ask for the invoice number as the payment reference. Send the PDF on the day the work finishes; late invoices are paid late. A proforma up front is the cleanest way to ask for a deposit.
Fixing a mistake
Never edit or delete an invoice you have sent. Issue a credit note that references the original number, states the reason and reverses the same GST, then issue a new invoice if needed. The Singapore credit note generator does this.
Questions people ask
Do I need to be registered to send an invoice?
You need a UEN; registration for GST is only needed if you charge it. Many small businesses invoice without charging GST.
Can I invoice in a foreign currency?
Usually yes for export clients, but Inland Revenue Authority of Singapore (IRAS) generally wants the GST amount, and sometimes the total, shown in Singapore Dollar at the official rate on the invoice date. Show both.
Is a PDF invoice legally valid in Singapore?
Where Singapore has no mandatory e-invoicing, yes: an emailed PDF with the required fields is a valid invoice. Where electronic issuance is required, the official system's document is the fiscal invoice and the PDF supports it.
What is the difference between an invoice and a receipt?
An invoice asks for payment and creates the debt; a receipt confirms payment received. Issue the invoice first, then a receipt or a marked-paid copy when the money arrives.
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 Inland Revenue Authority of Singapore (IRAS) 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 Inland Revenue Authority of Singapore (IRAS).
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Tools for Singapore
Invoices, quotations, purchase orders, credit notes and waybills in SGD, with GST and the UEN on the document. Plus a GST calculator and a salary tax calculator. Everything runs in your browser and nothing is uploaded.