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GST calculator: add or remove 10% GST
Take the GST out of a GST-inclusive price, or add GST to a price before GST. Worked in whole cents and rounded the way the GST law says, with the working shown. Nothing you type leaves your browser.
Type an amount to see the GST, the price before GST and the price including GST.
Several items on one invoice?
Paste one GST-inclusive line amount per row (a description on the same row is fine; the last amount on each row is used). The law lets you round the GST once on the invoice total or line by line, and the two can differ by a few cents.
The formulas
Removing GST: GST = GST-inclusive price ÷ 11, and the price before GST is the rest. The Australian Government’s Tax, Super + You guide to GST on purchases uses A$352 ÷ 11 = A$32, and warns against dividing by 10.
Adding GST: GST = price before GST × 10%, so the GST-inclusive price is the price before GST × 1.1.
Rounding: round the GST to the nearest cent, rounding half a cent up. For several taxable items on one invoice, you can total the unrounded GST and round once, or round each item and add them (the ATO calls these the total invoice rule and the taxable supply rule). Sources: ATO, Tax invoices (rounding of GST) and GST Act section 9-90.
A correct GST figure only matters if the supplier was registered for GST when they invoiced you. The ATO’s When you can claim a GST credit page says to make sure your suppliers are registered. Check a supplier’s GST registration, or check a quarter’s bills before the BAS.
Common questions
How do I work out the GST in a GST-inclusive price?
Divide the GST-inclusive price by 11. For example, A$352 including GST has A$32 of GST in it, and A$320 is the price before GST. Dividing by 10 is a common mistake: 10% is applied to the price before GST, so the GST is one-eleventh of the price after GST.
How do I add GST to a price?
Multiply the price before GST by 10% to get the GST, or by 1.1 to get the GST-inclusive price. A$320 plus GST is A$32 of GST, A$352 in total.
How is GST rounded?
To the nearest cent, with half a cent rounding up. When an invoice has several taxable items, the GST law (section 9-90 of the GST Act) allows either working out the GST on each item without rounding, adding them and rounding the total, or rounding each item to the decimal places your accounting system records and then rounding the sum. The calculator shows both, so you can see why an invoice can be a cent or two different from your own figure.
Can every business charge GST?
No. Only a business registered for GST can include GST in its prices. The ATO says to make sure your suppliers are registered for GST before you claim a GST credit. ClearABN's free GST check shows a supplier's registration today or on the date of an invoice.
What about GST-free items on the same invoice?
Only include the taxable items. GST-free items have no GST in them, so dividing a mixed total by 11 overstates the GST. A tax invoice has to show the extent to which each sale on it is taxable.
Is this tax advice?
No. It's arithmetic at the 10% GST rate. It doesn't decide whether a sale is taxable or whether you can claim a GST credit.
More: tax invoice checker · GST registration check · ABN lookup · check a supplier list