Free tool
GST calculator
Add 10% or take it back out. The second one is where people go wrong.
GST in Australia is 10%. That makes adding it easy and removing it slightly less easy, which is why almost every GST mistake runs in the same direction.
Adding GST
Multiply by 1.1. A job priced at $1,000 before GST invoices at $1,100, of which $100 is GST.
Removing GST
Divide the total by 11 to get the GST, or by 1.1 to get the price before GST. A $1,100 invoice contains $100 of GST and $1,000 of work.
The mistake is dividing by 10 instead of 11. Ten per cent of $1,100 is $110, but the GST in that invoice is $100, because the 10% was added to $1,000 and not to $1,100. Taking 10% off a GST inclusive figure overstates the GST every time, and on a large invoice it is not a rounding error.
Quick reference
| You have | You want | Do this |
|---|---|---|
| Price before GST | GST amount | Multiply by 0.1 |
| Price before GST | Total including GST | Multiply by 1.1 |
| Total including GST | GST amount | Divide by 11 |
| Total including GST | Price before GST | Divide by 1.1 |
What is not subject to GST
Some things are GST free rather than taxed at zero, and the distinction matters on a BAS. Basic food, most health and medical services, most education, and some childcare are GST free. Residential rent and most financial supplies are input taxed, which is different again.
For the trades and services in this directory, almost everything is taxable at 10%, so the calculator above covers it. If you are working out GST on something unusual, the Australian Taxation Office publishes the categories and that is the source to use.
Whether the business should be charging it at all
A business only charges GST if it is registered for GST. Registration is compulsory once turnover reaches the threshold the ATO sets, and optional below it, so plenty of smaller sole traders are legitimately not registered and legitimately do not add a GST line.
If an invoice has a GST line on it, the business should be registered and the ABN on the invoice should show as registered for GST. That is worth thirty seconds on the ABN checker, because a GST line charged by a business that is not registered is not something you can claim, and it is not something they are entitled to keep.
Tax invoices
To claim a GST credit you generally need a valid tax invoice from the supplier. Above a low threshold set by the ATO it has to carry the words "tax invoice", the seller name and ABN, the date, what was supplied, and the GST amount or a statement that the total includes GST. A handwritten total on a docket is not a tax invoice.
Common questions
How do I remove GST from a price?
Divide the GST inclusive total by 11 to get the GST, and by 1.1 to get the price before GST. A $1,100 total contains $100 of GST. Do not take 10% off the inclusive figure, because that gives $110 and overstates the GST.
Why divide by 11 and not by 10?
Because the 10% was added to the pre GST price, not to the total. If the price before GST is 10 parts, the GST is 1 part and the total is 11 parts. So the GST is one eleventh of the total, which is a division by 11.
What is the GST rate in Australia?
10%, and it has been 10% since GST started in July 2000. It applies to most goods and services, with GST free categories including basic food, most health and medical services and most education.
Does every business have to charge GST?
No. A business only charges GST if it is registered for GST, and registration is compulsory only once turnover reaches the ATO threshold. Below that it is optional, so a smaller sole trader may legitimately not charge it. If there is a GST line on the invoice, the ABN should show as registered for GST.
Is this calculator sending my figures anywhere?
No. It is arithmetic that runs in your browser. Nothing leaves the page, there is no request, and there is nothing to log.