GST Calculator Australia 2026

How Does GST Work in Australia?

GST is a flat 10% tax on most goods, services, and other items sold or consumed in Australia. It was introduced on 1 July 2000.

Registered businesses add GST to their prices and collect it on behalf of the Australian Taxation Office (ATO). You are effectively acting as a collector for the tax office — GST you collect is not part of your business revenue, and you must return it to the ATO when lodging your BAS.

While most items are subject to GST, some are GST-free. This includes basic food items, medical services, and certain educational courses. For a typical subcontractor or sole trader, however, nearly all labour and materials you sell will require GST.

How to Add GST to a Price

Adding GST to a quote or price is straightforward. Since the tax rate is 10%, you simply multiply your base rate by 1.10.

Alternatively, you can multiply the base amount by 0.10 to find the GST component, and then add that figure to your base price.

Worked Example:

You are quoting a bathroom reno at $5,500 for labour. The customer needs the GST-inclusive price.
- Multiply the base price by 1.10: $5,500 × 1.1 = $6,050.
- The GST component is $6,050 - $5,500 = $550.
The customer pays $6,050, and you must report the $550 GST on your next BAS.

How to Remove GST from a Total (Extract GST)

Removing GST from a receipt total is a common task when tracking expenses. To find the base cost before GST, divide the total price by 1.10.

Do not multiply the total by 10% to find the GST amount. That is a common error which gives an incorrect result. The GST component represents 1/11th of the total price, not 1/10th.

Worked Example:

You purchase an angle grinder from Bunnings for $330 (inclusive of GST).
- Divide the total by 1.10 to find the ex-GST base: $330 ÷ 1.1 = $300.
- Subtract the base from the total to find the GST paid: $330 - $300 = $30.
The GST component is $30, which is the input credit you claim back to reduce your ATO debt.

When Do You Have to Register for GST?

You must register for GST with the ATO if:

• Your business turnover (gross income minus GST) reaches or is expected to reach $75,000 in a 12-month period.
• You start a new business and expect turnover to meet or exceed that threshold in the first year.
• You provide taxi or ride-share services, in which case you must register regardless of turnover.

If your turnover is below $75,000, registering is optional. Some tradies choose to register anyway so they can claim GST back on startup costs (like tools and work vehicles). However, registering means you must add GST to all your customer invoices.

If you are close to the threshold, check out our all-in-one calculator to plan your charge-out rates.

Understanding Your BAS — What Sole Traders Need to Know

If you register for GST, you must file a Business Activity Statement (BAS) regularly (typically quarterly).

On your BAS, you declare:
- The total GST you collected from your clients (GST on sales).
- The total GST you paid to suppliers (GST on purchases).
Your final obligation is the difference: GST Collected - GST Paid.

If you collected more GST than you paid, you owe the ATO the difference. If you paid more GST than you collected (common when buying expensive gear or vehicles), the ATO will refund you. Use our **BAS GST Estimator** mode in the calculator above to check your current figures.

Common GST Mistakes Tradies Make

A few typical errors can cause issues with your accounting or lead to ATO penalties:

• Wrong formula: Multiplying a GST-inclusive total by 10% instead of dividing by 1.1 to extract the tax component.
• Late Registration: Forgetting to register once turnover crosses the $75,000 mark. The ATO can backdate your registration, making you liable for GST on past sales even if you didn't charge your clients for it.
• No Invoices: Claiming GST credits on expenses without keeping valid tax invoices. For purchases over $82.50 (inclusive of GST), you must have a tax invoice to claim the credit.
• Subbie Invoices: Claiming GST credits on payments to subcontractors who are not actually registered for GST. Always verify their ABN status.

GST on Subcontractor Invoices — Who Charges What?

When you engage subcontractors, how GST is handled depends on their registration status:

- If the subcontractor is registered for GST, they must charge you GST on their invoices. You pay the total and claim the GST portion back as an input credit on your BAS.
- If the subbie is not registered, they cannot charge GST. You pay the invoice total and claim no GST credits.

You can use our invoice generator to draft invoices with and without GST quickly.

GST-Free vs Input-Taxed — What's the Difference?

Understanding these categories is useful for general business tax knowledge:

- GST-free: You do not charge GST on these sales, but you can still claim credits on business expenses related to them (e.g., fresh food, exports).
- Input-taxed: You do not charge GST, and you cannot claim credits on expenses related to these sales (common in financial services and residential rent).