GST Calculator Australia 2026-27

How to add GST, and how to take it out

Two formulas cover every case. When the price you hold is GST-exclusive, the GST is 10% of it and the total is the price × 1.1. When the price is GST-inclusive, the GST is the price ÷ 11 and the value before GST is the price × 10 ÷ 11. The second formula is the one people get wrong, because it feels natural to take 10% off a total. On a $110 invoice that gives $11.00, while the GST really is $10.00: the 10% was charged on $100, not on $110.

The Act itself works the same way. Section 9-70 sets the GST at 10% of the value of a taxable supply, and section 9-75 defines that value as the price multiplied by 10/11. Its own example is a car sold for $22 000: value $20 000, GST $2 000. Our calculator applies those two sections literally, which is why the result for one item always matches the Act's example to the cent.

Why one item at a time is not enough

Real paperwork rarely holds a single price. A tradie's invoice has labour, parts and a call-out fee; a supermarket docket mixes GST-free bread with taxable cleaning products; a month of receipts arrives as a column in a spreadsheet. A single-box calculator forces you to run each line separately and add the results by hand, which is where the errors creep in. Here, each line keeps its own status. In the default example, $440.00 of consulting and $89.95 of printer cartridges carry $48.18 of GST between them, while $12.50 of bread and milk carries none, so the GST is not one-eleventh of the $542.45 total.

Switch the toggle at the top and every line flips between "my prices include GST" and "my prices exclude GST": useful when a supplier quotes ex GST and you want to see what the client will actually pay. The paste box turns a column copied from Excel, Google Sheets or a bank export into lines, ignoring dollar signs and thousands separators.

Rounding: what section 9-90 says about the cents

GST is paid in cents, so a fraction of a cent has to go somewhere. Section 9-90 of the Act gives the rule. For a single taxable supply on an invoice, the GST is rounded to the nearest cent, half a cent going up. For several supplies on the same invoice, you may either add the unrounded GST of each line and round the total once, or round each line to the precision of your accounting system and then add them up, rounding the sum to the nearest cent.

The two methods can differ. Three coffees at $0.95 each contain 0.0864 dollars of GST apiece. Rounded once on the invoice, the GST is $0.26; rounded per line, it is $0.27. The calculator uses the invoice-total method by default and tells you when the line method would give a different figure, so you can match what your point-of-sale system prints. The GST rounding rules page compares both on your own numbers.

Taxable, GST-free and input-taxed on the same invoice

Only a taxable supply carries GST. Division 38 of the Act makes many supplies GST-free: most basic food (section 38-2, with exceptions for restaurant meals, hot takeaway and the foods listed in Schedule 1), medical and health services, education courses, childcare and exports. Division 40 makes others input-taxed: financial supplies such as interest and fees on loans, and residential rent. In both cases the customer pays no GST. The difference is on the seller's side: a GST-free seller still claims credits for the GST in its costs, an input-taxed seller does not. Mark each line accordingly and the calculator leaves it out of the GST total. More detail, with a simulator of the credits you keep or lose, on GST-free and input-taxed sales.

GST values and parameters for 2026-27

GST on common amounts

Each row is produced by the same engine as the calculator, rounded to the cent under section 9-90(1).

Who charges GST in the first place

You charge GST only if you are registered for it, or required to be. Registration becomes compulsory when your GST turnover reaches $75 000 ($150 000 for a non-profit body), measured over the current month and the previous eleven, or over the current month and the next eleven. Taxi, limousine and ride-sourcing drivers must register from the first dollar, and so must anyone who wants to claim fuel tax credits, according to business.gov.au. Below the threshold, registering is a choice that brings both the obligation to charge GST and the right to claim credits. The GST registration threshold page tests both turnover measures on your figures, including the GST-free sales that count and the input-taxed ones that do not.

Tax invoices: the $82.50 line

To claim a GST credit on a purchase you generally need a tax invoice. Section 29-80 of the Act, with regulation 29-80.01, lifts that requirement when the value of the supply is $75 or less, which is $82.50 once GST is added. Below that line, a docket or receipt is enough; above it, ask the supplier for a tax invoice showing their ABN and the GST, or the credit can be refused. The GST on $100 page works through a purchase just above the line.

Everything else you can calculate here

• Reverse GST calculator: Take the GST out of a receipt total, even when part of it is GST-free.
• GST inclusive vs exclusive: Which price to quote, which to display, and how to convert one into the other.
• GST registration threshold: $75 000, or $150 000 for non-profits: test your current and projected turnover.
• BAS and GST credits: Estimate 1A, 1B and the net GST of your quarter, with its due date.
• GST-free and input-taxed sales: Food, health, rent, interest: what carries GST and which credits you lose.
• GST on imports: Low value goods up to $1 000 versus GST at the border.
• GST for sole traders: Register or not, raise your price or absorb the tax.
• GST rounding rules: Round each line or the invoice total: the cents the law allows.
• GST on $100: The $82.50 line above which you need a tax invoice.
• GST on $1 000: The low value import threshold, and what changes one dollar above it.

Three mistakes we see on invoices

1. Charging GST without being registered. An invoice that shows GST from a business that has no GST registration overstates the price, and the customer cannot claim the credit. Check the ABN Lookup before you add 10%.
2. Dividing a mixed receipt by 11. A grocery docket with fresh food on it contains less GST than one-eleventh of the total. Split the lines, or use the reverse GST calculator with its GST-free field.
3. Claiming the full credit on a purchase used partly in private. Section 11-30 reduces the credit to the business share. A phone used half for work gives half the GST back, which the BAS simulator lets you set.

This calculator gives estimates based on the law as it stood on 2026-10-03. It does not replace the ATO's decision or advice from a registered tax or BAS agent, particularly for margin scheme property sales, going concerns or GST groups, which follow special rules it does not model.