Guide
GST on Quotes and Invoices in Australia
A lot of GST confusion comes down to one simple issue: people are not always looking at the same type of number. If one figure is GST-inclusive and the other is GST-exclusive, the comparison breaks immediately.
In this guide
- Know whether the amount already includes GST.
- Adding GST and removing GST are different checks.
- Clear quote wording prevents avoidable confusion.
Last updated
27 April 2026
Category
GST & Tax
Use with
3 related calculators
Guide
First decide whether the amount is GST-inclusive or GST-exclusive
Before you calculate anything, work out what kind of number you are holding. If the amount is GST-exclusive, GST still needs to be added. If it is GST-inclusive, part of that total already belongs to GST.
Most confusion happens when a customer, staff member, or spreadsheet is comparing those two types of numbers as if they were the same.
Adding GST and removing GST are not the same calculation
When you add GST to a standard taxable sale, you calculate 10% of the GST-exclusive amount and add it on top.
When you remove GST from a GST-inclusive total, you do not simply subtract 10% of the total. You first work back to the net amount because the GST portion is one-eleventh of the GST-inclusive price.
Simple GST checks
- Add GST: GST = net amount x 10%, gross amount = net amount + GST
- Remove GST: net amount = gross amount / 1.1, GST = gross amount - net amount
Keep quotes and invoices consistent
If you price work internally on an ex-GST basis, keep that number visible until the final stage, then add GST clearly to the customer total if it applies.
That makes the quote easier to explain and reduces the risk of accidentally comparing ex-GST cost figures to inc-GST sales totals.
- Be clear whether the displayed amount includes GST.
- Use the same approach across quotes, variations, and final invoices.
- Check the total before sending so the GST treatment is obvious and consistent.
Watch the common small-business mistakes
The mistakes are usually simple: mixing inc-GST and ex-GST numbers, forgetting GST on variations, or collecting GST but failing to set it aside for BAS.
A quick calculator check before the document goes out is often enough to catch those errors early.
This guide focuses on common 10% taxable sales. Some supplies can be treated differently, so always check the actual GST treatment if the sale is not a standard taxable one.
Worked example
See it in a realistic business scenario
Use the example below as a quick sense check before you apply the same logic to your own pricing, payroll, quoting, or tax workflow.
Worked example
Worked example: adding and removing GST
A business is checking a $2,500 ex-GST quote and also wants to reverse-check the GST from a $2,750 inc-GST invoice total.
- GST-exclusive amount: $2,500
- GST-inclusive amount: $2,750
Calculation steps
- Add GST to the quote: $2,500 x 10% = $250 GST, so the total becomes $2,750.
- Remove GST from the invoice total: $2,750 / 1.1 = $2,500 net amount.
- GST portion = $2,750 - $2,500 = $250.
Both checks lead to the same answer when the sale is a standard 10% taxable one: $2,500 net, $250 GST, $2,750 gross.
Important note
Use the guide as a practical reference, not as advice
This page is designed to support better commercial decisions, but it should not be treated as a substitute for professional advice.
Important note on GST treatment
This guide is a practical overview for common quote and invoice checks. It is not tax advice, and it does not cover every GST treatment or exemption.
- Use these examples for standard taxable sales only unless you have confirmed the GST treatment separately.
- Invoices and tax obligations can depend on the nature of the sale, registration status, and record-keeping requirements.
- If the GST treatment is unclear, confirm it with the ATO or a registered tax or BAS professional before relying on the result.
Related tools
Use the calculators that connect to this guide
These linked tools help you turn the ideas in the guide into a faster number check or a cleaner pricing decision.
GST Calculator Australia
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