data tool
GST calculator for Singapore
Singapore GST has been 9% since 1 January 2024: multiply a price by 1.09 to add it, or multiply a GST inclusive price by 9/109 to find the GST inside it. This calculator does both line by line, keeps zero rated and exempt lines at nothing, and says whether the sale can go on a simplified tax invoice.
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- Runs on your device, nothing is uploaded
- Free, no sign in
- No watermark, no file limit
How it works
- 1
Pick the direction
Choose whether the amounts you type exclude GST, so 9% is added, or include it, so the GST is taken out with 9/109.
- 2
Enter the lines
Type each amount and set it to 9% standard or to zero rated or exempt. Add lines for a whole invoice, up to 20.
- 3
Read the totals
The panel shows the total before GST, the GST and the total including GST, to the cent.
- 4
Check the invoice note
Below the lines, a note says whether a simplified tax invoice is allowed at that total or a full tax invoice is needed.
Why the fraction is 9/109
GST is 9% of the value before tax. Once it has been added, the price is 109% of that value, so the GST is 9 parts out of 109, not 9% of the total. On a S$109 price the GST is S$9 and the value before GST is S$100. Taking 9% of S$109 would wrongly give S$9.81. The same rule works for any GST inclusive amount: multiply by 9/109 for the GST, or divide by 1.09 for the price before it. Going the other way, multiplying by 1.09 adds GST to a price that does not include it yet.
Showing GST inclusive prices to customers
A GST registered business that displays or quotes prices to the public in Singapore must show them inclusive of GST, according to IRAS. A menu, a price list or a shop shelf therefore carries the final price, and a quote to a consumer should do the same. Business customers often want the split as well, so a quote to another company commonly shows the price before GST, the GST and the total. Run the calculator in the include direction to find the split behind a displayed price, or in the exclude direction to build a display price from a cost.
Full and simplified tax invoices
A full tax invoice carries the supplier's name, address and GST registration number, an identifying number, the date, the customer's name and address, a description of the goods or services, the total before GST, the GST rate and amount, and the total including GST. IRAS allows a simplified tax invoice when the total payable, GST included, is S$1,000 or less; it can leave out the customer details and show only the total including GST with a statement that it includes GST. The note under the calculator applies that S$1,000 line to the total you type.
Zero rated and exempt lines
Exports of goods and international services are zero rated: GST is charged at 0%, and the supplier can still claim GST on its own purchases. Exempt supplies, such as the sale and lease of residential property and most financial services, carry no GST and do not let the supplier claim the input tax tied to them. On an invoice both show no GST, which is why the calculator has one setting for them, but they are not the same thing for your GST return. Keep a note of which rule each line follows.
Rounding to the cent
GST is worked to the cent, rounding half a cent up. When an invoice has several standard rated lines, adding them first and rounding the GST once matches the total on the invoice; rounding each line and adding the rounded figures can leave a difference of a cent or two on a long invoice. The calculator adds the 9% lines together and rounds once, and shows each line's GST only as a guide. A one cent difference from an accounting system that rounds per line is normal.
Putting the split on a quote
A quote to a business should show the price before GST, the GST and the total, so the buyer can see what it will claim back; a quote to a consumer shows the GST inclusive price. The proposals module sets a tax rate on each line of its pricing table and labels the tax line Tax when the currency is not AUD, NZD, GBP or EUR, so set the rate to 9% on each line of a Singapore dollar quote and the split from this calculator carries straight into the document the client accepts.
Limits
- Rate checked on 21 October 2026 against IRAS. This is arithmetic, not tax advice.
- Lines at the same rate are added before the GST is worked out and rounded once to the cent, half a cent up.
- No reverse charge, no overseas vendor registration, and no 7% or 8% periods from before 2024.
- Whether a supply is zero rated or exempt is your call; the tool only applies the choice made on each line.
What it does not do
- It does not prepare or file a GST return.
- It does not tell you whether you must register for GST.
- It does not store the amounts.
Questions people ask
How do I work out GST from a total in Singapore?
Multiply the GST inclusive total by 9 and divide by 109. On S$545 the GST is S$45 and the value before GST is S$500. Dividing the total by 1.09 gives the value before GST in one step. Taking 9% of the total gives the wrong answer, because the total already contains the tax.
When did Singapore GST become 9%?
The rate went from 7% to 8% on 1 January 2023 and from 8% to 9% on 1 January 2024. A supply that straddles a rate change can have special time of supply rules, which this calculator does not apply; it uses 9% throughout, the rate IRAS lists as current.
Can I issue a simplified tax invoice for every sale?
Only when the total payable including GST is S$1,000 or less. Above that, a GST registered customer needs a full tax invoice to claim the input tax. Retailers often give receipts that double as simplified tax invoices for small sales and issue a full tax invoice on request for larger ones.
Must prices shown to customers include GST?
Yes, for prices displayed or quoted to the public by a GST registered business. IRAS requires the price shown to include GST, so a customer sees what they will pay. Showing a price before GST with a separate note is not enough for consumer facing displays, though business quotes can show the split as well.
Do I charge GST if my business is not registered?
No. Only a GST registered business may charge GST and issue tax invoices. A business that is not registered sells at its price with no GST line. Registration becomes compulsory once taxable turnover passes the threshold IRAS sets, and some businesses register voluntarily below it.
Why does the line GST not add up to the total GST?
Because of rounding order. Each line's GST is rounded to the cent for display, while the total GST is worked out once on the sum of the lines at 9%. On an invoice with many lines those two methods can differ by a cent or two. The total shown is the one that matches a single rounding.
Put the GST split on a quote
Take what you made here into proposals.
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Background reading: the question page on this.
Written and checked by the OneCraft team. Last checked .