For a fully taxable sale at the standard 10% rate, add GST by multiplying the GST-exclusive amount by 1.1. To find the GST included in a GST-inclusive price, divide the total by 11.
What this means in practice
For example, a $100 GST-exclusive price becomes $110 including GST. The GST component of $110 is $10. Dividing a GST-inclusive amount by ten is incorrect because the price already includes the tax. These calculations apply only where the sale is taxable at 10%. GST-free and input-taxed supplies need different treatment, and a business must not assume every invoice contains claimable GST.
Your next steps
- Check whether the sale is taxable
- Identify whether the price includes GST
- Use the correct calculation
- Keep the supporting invoice
Get help with the next step
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Official guidance: ASIC Moneysmart: GST calculator ↗
General information prepared on 26 September 2026. Rules and individual circumstances can change. Confirm the treatment that applies to you before acting.
Prepared by the Affordable Bookkeeper content team. Our services and practitioner arrangements.
