GST Calculator Australia

GST (Goods and Services Tax) in Australia is a flat 10% tax applied to most goods and services (ATO — How GST works). To add GST, multiply the price by 1.1. To remove GST from an inclusive price, divide the total by 11 to find the GST component. The calculator above handles both operations, with support for multiple line items.

How do you calculate GST in Australia?

The Australian GST rate is 10%, which makes the arithmetic straightforward. There are two common calculations depending on whether you are working with a price before or after GST.

Adding GST to a price

When you know the price excluding GST and need to find the GST-inclusive total:

GST amount = price (ex-GST) x 0.10

Total (inc-GST) = price (ex-GST) x 1.10

Worked example: You are quoting a service at $850 excluding GST.

• GST = $850 x 0.10 = $85.00
• Total including GST = $850 + $85 = $935.00

Removing GST from an inclusive price

When you have a GST-inclusive amount and need to find the price before GST:

GST amount = total (inc-GST) / 11

Price (ex-GST) = total (inc-GST) - GST amount

Worked example: You receive a GST-inclusive receipt for $1,320.

• GST = $1,320 / 11 = $120.00
• Price excluding GST = $1,320 - $120 = $1,200.00

The “divide by 11” shortcut works because the GST-inclusive price is 110% of the original (11 parts total), and GST is 1 of those 11 parts.

Who needs to register for GST?

Not every Australian business needs to register for GST. Registration depends on your annual GST turnover and the type of business you operate.

GST registration thresholds

GST turnover is your gross business income (total sales), not your net profit. If your turnover reaches the threshold in any 12-month period (not just the financial year), you must register within 21 days (ATO — Registering for GST).

If your turnover is below the threshold, you can still register voluntarily. Voluntary registration lets you claim GST credits on business purchases, but you must also charge GST on your sales and lodge BAS returns.

What happens if you do not register when required?

The ATO can register you automatically and may impose penalties. You may also be liable for GST on sales made since the date you were required to register, even if you did not charge GST to your customers.

What goods and services are GST-free?

Not everything in Australia attracts GST. The GST Act distinguishes between three categories of supplies.

Taxable supplies (10% GST applies)

Most goods and services fall into this category: commercial products, professional services, restaurant meals, clothing, electronics, new residential property, and commercial property.

GST-free supplies (0% GST)

These items are not subject to GST, and businesses that sell them can still claim GST credits on related purchases:

• Basic food — fresh fruit, vegetables, meat, bread, milk, eggs, and other unprocessed staples
• Health services — medical consultations, hospital treatments, dental services, allied health
• Education — courses leading to qualifications at universities, TAFEs, and registered training organisations
• Childcare — approved childcare services
• Exports — goods and services exported from Australia
• Some charitable activities — certain supplies by endorsed charities

Input-taxed supplies (no GST charged, no credits claimed)

These are not technically GST-free. The seller does not charge GST, but also cannot claim GST credits on related purchases:

• Residential rent — rental income from residential investment properties
• Sales of existing residential properties — but new residential property sales do include GST
• Financial supplies — bank interest, loan fees, share trading

This distinction matters for property investors: because residential rent is input-taxed (not GST-free), landlords cannot claim back the GST included in property management fees, repairs, or other expenses. The GST component becomes part of the cost.

How does GST work with BAS?

If your business is registered for GST, you must lodge a Business Activity Statement (BAS). The BAS reports the GST you have collected on sales and the GST credits you can claim on purchases. The difference determines whether you owe the ATO or receive a refund. The BAS Calculator estimates the net GST payable or refund for a quarterly BAS.

BAS lodgement frequency

Some businesses that are voluntarily registered for GST may be eligible to report annually.

What you report on your BAS

At a minimum, the GST section of your BAS includes:

• 1A — GST on sales (GST you collected from customers)
• 1B — GST on purchases (GST credits you can claim)
• The difference between 1A and 1B is the amount you owe (or the refund you are due)

BAS is usually due 28 days after the end of the reporting period (ATO — BAS due dates). Late lodgement or payment may result in penalties and interest charges from the ATO.

GST for property investors

Property investors encounter GST in specific situations that differ from most businesses.

Residential rent is input-taxed. This means no GST is charged on residential rent, and landlords cannot claim GST credits on expenses related to the rental property (ATO — GST-free sales). The GST paid on property management fees, insurance, repairs, and maintenance is a genuine cost that cannot be recovered.

New residential property attracts GST. If you purchase a brand-new home or apartment from a developer, the purchase price generally includes GST. The margin scheme may apply, which can reduce the GST payable by the developer and therefore the purchase price.

Commercial property attracts GST. If you invest in commercial property, the sale and lease are taxable supplies. This means GST applies to rent and the sale price, but you can also claim GST credits on related expenses.

For residential property investors, the main impact of GST is that it increases the effective cost of property management and maintenance by approximately 9.09% (the GST component embedded in GST-inclusive invoices that cannot be claimed back).

Common GST calculation mistakes

These are the most frequent errors businesses make with GST calculations:

1. Calculating 10% of the GST-inclusive amount instead of dividing by 11. If you take 10% of $110, you get $11 — but the correct GST component is $10 ($110 / 11). This is because 10% applies to the original price, not the total.

2. Forgetting that some items are GST-free. Not every line on an invoice attracts GST. Mixed invoices with both taxable and GST-free items require the GST to be calculated only on the taxable portion.

3. Not keeping valid tax invoices. To claim GST credits, you need a tax invoice. For purchases over $82.50 (inc-GST), the tax invoice must include the supplier’s ABN, GST amount, and other details specified by the ATO.

4. Including GST in income when it should not be counted. GST collected is not your income — it belongs to the ATO. When calculating your business turnover for the GST threshold, include the GST-exclusive amount of your sales.