GST calculator

Add or remove GST correctly, work out the net amount for your BAS, and check whether registration is compulsory.

Covers 2026-27 · rates as at 2026-07-01

2026-27

GST

Estimate

$100.00

Divide the GST-inclusive price by 11 — never take 10% off

Price before GST: $1,000.00
Price including GST: $1,100.00
Net GST on your BAS: $100.00

Price composition

Breakdown of GST
GST-inclusive amount entered	$1,100.00
GST component	$100.00
Net GST payable	$100.00

To remove GST, divide by 11. Taking 10% off a GST-inclusive price gives the wrong answer every time.
Registration is compulsory once turnover reaches $75,000, or $150,000 for non-profits.

To remove GST from $1,100 you divide by 11, giving $100 of GST and $1,000 before tax. Taking 10% off would give $990 — wrong by $10.

Export your real numbers to Sheets

GST

Estimate

$100.00

Divide the GST-inclusive price by 11 — never take 10% off

Price before GST: $1,000.00
Price including GST: $1,100.00
Net GST on your BAS: $100.00

Price composition

Breakdown of GST
GST-inclusive amount entered	$1,100.00
GST component	$100.00
Net GST payable	$100.00

To remove GST, divide by 11. Taking 10% off a GST-inclusive price gives the wrong answer every time.
Registration is compulsory once turnover reaches $75,000, or $150,000 for non-profits.

To remove GST from $1,100 you divide by 11, giving $100 of GST and $1,000 before tax. Taking 10% off would give $990 — wrong by $10.

How this is calculated

Divide by 11, never subtract 10%

GST is 10% of the price before tax, so it is one eleventh of the price after tax. On $1,100 the GST is $100, not the $110 that taking 10% off would suggest. The gap grows with every invoice you process.

GST = inclusive ÷ 11; ex-GST = inclusive × 10 ÷ 11

BAS reports net, not gross

You remit GST collected on sales less credits on business purchases. $5,000 of GST collected against $22,000 of GST-inclusive purchases leaves $3,000 payable, because those purchases carry $2,000 of credits.

net GST = GST on sales − GST on purchases

Registration is compulsory at $75,000

Once projected or actual turnover reaches $75,000 you must register within 21 days, or $150,000 for a non-profit. Ride-share and taxi drivers must register from the first dollar regardless of turnover.

Worked example: Removing GST from an $1,100 invoice

Inputs
Amount	$1,100
Mode	Remove GST

Result
GST	$100
Before GST	$1,000
Divisor	11

The common error — taking 10% off $1,100 — gives $990 and $110 of GST. Across a year of invoicing that misstates both your income and your BAS.

What this assumes

A standard 10% taxable supply.
Not GST-free or input-taxed.
Registered for GST on an accruals basis.
All purchases carry a valid tax invoice.

Where this commonly goes wrong

Basic food, most health and medical services and education are GST-free, so charging 10% on them overcollects and creates a liability you then have to refund.
Residential rent is input-taxed: no GST is charged and no credits can be claimed on the costs, which is different from being GST-free.
Claiming a credit without a valid tax invoice above $82.50 is not allowed, and it is the most common adjustment the ATO makes on review.

Questions

How do I remove GST from a price?

Divide the GST-inclusive amount by 11. On $1,100 that gives $100 of GST and $1,000 before tax. Taking 10% off is the common mistake and gives $990, understating the pre-tax price by $10.

How do I add GST to a price?

Multiply by 1.1, or add 10%. $1,000 before GST becomes $1,100. Adding and removing are not symmetrical operations, which is exactly why the divide-by-11 rule exists.

When do I have to register for GST?

Once your turnover reaches $75,000, or is projected to, you must register within 21 days. Non-profits register at $150,000, and ride-share and taxi drivers must register from the first dollar.

What goes on my BAS?

GST collected on sales less GST credits on business purchases. $5,000 collected against $22,000 of GST-inclusive purchases leaves $3,000 to remit, because those purchases carry $2,000 of credits.

What is GST-free versus input-taxed?

GST-free supplies — basic food, most health and education — carry no GST but still allow credits on your costs. Input-taxed supplies such as residential rent carry no GST and allow no credits at all.

Do I need a tax invoice to claim a credit?

For purchases above $82.50 including GST, yes. Claiming without one is not permitted and is the most frequent adjustment made on review, so the invoice matters as much as the payment.

Related tools

Sources

General estimate based on published ATO rates for the 2026-27. Not tax advice, and it does not consider your objectives, financial situation or needs. Confirm your position with the ATO or a registered tax agent.