Add or remove 10% Australian GST from any amount. Uses the correct /11 formula for reverse GST calculation.
Australian GST Calculator — 10%
Ex-GST Amount
GST Amount (10%)
Inc-GST Amount
The /11 formula: To find GST in a GST-inclusive price, divide by 11.
Example: $110 inc-GST ÷ 11 = $10 GST | $110 - $10 = $100 ex-GST.
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How Australian GST Works
Australia introduced the Goods and Services Tax (GST) on 1 July 2000 at a flat rate of 10%. It is administered by the Australian Taxation Office (ATO) and applies to most goods, services, and other items sold or consumed in Australia.
The /11 Reverse GST Formula
The easiest way to extract GST from a GST-inclusive price is to divide by 11. This works because a $100 item with 10% GST becomes $110 (= 11/10 × 100). So $110 ÷ 11 = $10 GST. The ex-GST amount is the total minus the GST: $110 − $10 = $100.
GST-Free and Input-Taxed Supplies
GST-free (0%): Basic food (not restaurant meals), exports, most medical and educational services, water and sewerage, childcare, some religious services
Input-taxed: Financial services (bank fees, insurance premiums), residential rent, sale of second-hand residential property (where no GST was charged when built)
Taxable (10%): Everything else — new homes, commercial property, professional services, retail, restaurants, new cars
GST Registration Threshold
Businesses must register for GST if their GST turnover exceeds AUD $75,000 per year ($150,000 for non-profit bodies). Ride-share and taxi drivers must register regardless of turnover. Registration is done through the ATO Business Portal or myGovID.
Frequently Asked Questions
To add 10% GST: multiply the ex-GST price by 1.10. To find the GST in a GST-inclusive price: divide the total by 11. To find the ex-GST price: divide the total by 1.10, or subtract the /11 figure from the total. Example: $550 inc-GST ÷ 11 = $50 GST | $550 − $50 = $500 ex-GST.
A tax invoice is required for all taxable sales over $82.50 (inc-GST). It must include: the words 'Tax Invoice', the seller's name and ABN, the date, a description of what was sold, the GST-inclusive price, and either the GST amount separately or a statement that the price includes GST. For sales over $1,000, the buyer's identity must also be included.
Residential rent is input-taxed — no GST applies and the landlord cannot claim GST credits on related expenses. Commercial rent (offices, retail, warehouses) is subject to 10% GST, and the landlord must be GST-registered and issue tax invoices. Business tenants can claim the GST back as an input tax credit.
An Australian Business Number (ABN) is an 11-digit identifier issued by the ATO to businesses. You need an ABN to register for GST. Suppliers without an ABN can have 47% withholding tax deducted from payments to them. Even if under the $75,000 GST threshold, having an ABN is strongly recommended for any freelancer or business.