Tax Invoice
If you’re GST-registered in Singapore, there’s no getting around it — when you sell to another GST-registered business, a tax invoice has to be issued. This isn’t just a courtesy or “good business practice”; it’s the official proof your customer needs to claim input tax on standard-rated purchases.
And here’s the part many forget — there’s a time limit. The invoice must go out within 30 days from the time of supply. That “time of supply” isn’t whenever you get to it. It’s when the goods are delivered or the service is performed. Wait too long, and you’re not only inconveniencing your customer but also risking compliance trouble.
One more golden rule: only one original tax invoice per transaction. If that gets lost, yes, you can issue another — but it must be marked clearly as “Copy” or “Duplicate” so no one tries to claim GST twice on the same deal.
You can skip the tax invoice entirely in certain cases, like:
- Zero-rated supplies.
- Exempt supplies.
- Deemed supplies.
- Sales to a non-GST registered customer.
Still, even if you decide to issue one for a zero-rated supply, you can’t just throw something together. It needs every required detail, and it must say GST is charged at 0%.
And here’s a common mistake: for invoices over $1,000 (GST included), you can’t just put “Cash” instead of the customer’s name and address. That’s not acceptable, and it’s an easy way to get flagged.
The tax invoice is more than a bill — it’s a compliance tool. To keep it valid, certain particulars must be present. These include:
- The phrase “tax invoice” prominently displayed.
- A unique identifying number (your invoice number).
- The date you issue it.
- Your name, address, and GST registration number.
- Any cash discount offered.
- The customer’s name and address.
- A clear description of goods or services, including the type of supply.
- The quantity of goods or extent of services.
- The amount payable before GST.
- The total amount payable, including GST.
- The total amount excluding GST, the GST rate, and the GST amount shown separately.
- A breakdown showing exempt, zero-rated, or other supplies, with the gross total for each.
If you miss any of these, it’s like leaving a puzzle with a missing piece — the picture doesn’t work. And in tax terms, that means the document might not be valid for claiming GST.
Simplified Tax Invoice
For smaller transactions — $1,000 or less including GST — there’s an easier way: the simplified tax invoice. Think of it as a slimmed-down version of the full invoice.
You don’t need the customer’s name here. What you do need is:
- Your name, address, and GST registration number.
- The total payable (GST included).
- A unique identifying number.
- The phrase “Price payable includes GST”.
It’s quicker to prepare and works perfectly for low-value sales, as long as you stick to the requirements.
Invoicing in a Foreign Currency
Sometimes, you’re selling locally but your customer wants the invoice in USD, EUR, or some other currency. That’s fine — but GST calculations still have to be shown in Singapore dollars for three things:
- The total before GST.
- The GST amount.
- The total including GST.
The exchange rate you use must come from a local bank or a rate published in a locally circulated newspaper. Picking random online rates? That’s a no-go.
And consistency matters. Once you choose your source, you have to use it for at least a year from the end of the accounting period in which you start. Update it at least every three months. The idea here is to avoid rate-hopping to get a “better” number — IRAS wants one standard approach.
Receipt
In some cases, you can issue a receipt instead of a tax invoice — usually when selling to someone who isn’t GST-registered, and only if they ask for it.
A proper receipt must include:
- A printed serial number.
- Your name and GST registration number.
- The date of issue.
- The total payable, GST included.
- The words “Price payable includes GST”.
If you don’t issue receipts, that doesn’t mean you skip recording the sale. Use a cash register, accounting software, or even a handwritten log if needed — just make sure there’s an audit trail.
Why the Rules Matter
Yes, it’s about compliance — but it’s also about keeping your business clean and your customers confident. Missing details, wrong exchange rates, or sloppy records don’t just cause IRAS issues; they waste your time fixing preventable mistakes.
During an audit, if IRAS sees inconsistent or incomplete invoices, they won’t just stop there — they might decide to look deeper into your business. Following these rules avoids that.
Final Thoughts
Basic invoicing rules might seem like they’re there to make life harder, but they’re actually your protection. They make sure every GST claim is supported, every transaction is transparent, and nothing looks suspicious.
The best approach? Treat invoicing as part of doing business, not an afterthought. Send them on time, fill in every detail, and keep your currency conversions consistent. Do it right once, repeat it every time, and it becomes second nature.
When invoices are complete and correct, you don’t just meet IRAS’s standards — you show customers that you run a tight, professional operation. And that’s a reputation worth keeping.
