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Australia · Simpler BAS

What goes in the GST boxes on your BAS

G1, 1A and 1B, worked out from your quarter — with GST-free sales handled properly, and both ways of stating G1 shown, because the form lets you choose and most tools do not.

Checked against the ATO

Checked against the legislation — how we check.

Are your figures GST-inclusive?

Basic food, most health and medical, education, exports. These go into G1 but never into 1A.

Business purchases you hold a tax invoice for. Leave out anything GST-free or input taxed. The GST on an asset comes back here; whether its cost is deductible at once is a separate question with its own threshold.

How will you state G1?

Net GST to pay

$6,000

$10,000 of GST on sales, less $4,000 of GST credits on purchases.

What to put on the form

G1 Total sales$110,000
1A GST on sales$10,000
1B GST on purchases−$4,000
Net amount to pay$6,000

G1 is stated including GST — indicate that on the form.

How the amount is worked out

This is the GST section only. Your statement may also carry PAYG withholding, PAYG instalments, FBT, luxury car tax, wine equalisation tax or fuel tax credits. General information, not tax advice.

G1 can be stated either way, and you have to say which

This is the part that trips people, because both answers are right and only one of them matches the box you ticked. The ATO’s bookkeeping guide says it directly: you disclose either the GST-inclusive or the GST-exclusive total sales figure at G1, and you must indicate your choice.

G1 stated both ways for the figures entered
How G1 is statedThe figure
Including GST$110,000
Excluding GST$100,000

Whichever you choose, 1A and 1B do not change — the GST is the GST.

GST-free sales belong at G1, not at 1A

A GST-free sale is still a sale. The ATO’s guide is explicit that GST-free sales are reported at G1 total sales; what they do not do is appear at 1A, because there is no GST on them to report. Leaving them out of G1 understates your turnover on the form; putting them into 1A overstates what you owe. Both are common, and they pull in opposite directions.

Three thresholds, two of them ten million

Small business GST has three turnover lines that decide three unrelated things, and two of them are the same number. It is worth having them side by side once:

The GST turnover thresholds and what each decides
ThresholdWhat it decides
$20,000,000Quarterly reporting, or compulsory monthly — how often you lodge.
$10,000,000Simpler BAS, or full reporting — how much detail you give.
$10,000,000The turnover cap for the December monthly due-date concession.

The BAS due dates page covers the frequency side and the concessions.

If you are on full reporting

At $10,000,000 of GST turnover or more, the GST section grows from three labels to seven. This calculator covers the Simpler BAS three; the rest are a matter of splitting the same totals:

Full reporting method labels
Label
G1 Total sales
G2 Export sales
G3 Other GST-free sales
G10 Capital purchases
G11 Non-capital purchases
1A GST on sales
1B GST on purchases

Businesses under the threshold paying quarterly instalments and reporting annually also complete 1H, the instalments already reported for the period.

Frequently asked questions

What goes at G1, 1A and 1B?
G1 is your total sales for the period, 1A is the GST on your sales, and 1B is the GST on your purchases. Those three are the whole GST section under Simpler BAS, which is the default for any business with a GST turnover under $10 million — you do not have to complete a GST calculation worksheet at all. What you pay, or get back, is 1A minus 1B.
Does G1 include the GST or not?
Whichever you tell it to. Take a quarter with $110,000 of GST-inclusive sales: G1 is $110,000 if you tick that it includes GST, or $100,000 if you tick that it does not, and 1A is $10,000 either way. Both are correct. The error is mixing them — entering the inclusive figure and ticking the exclusive box makes your GST look like 9.09% of sales rather than 10%, which is exactly the kind of mismatch that draws a question. Pick one, tick it, and keep doing it the same way every quarter.
Do GST-free sales go on the BAS?
Yes, at G1 — and only at G1. A cafe with $80,000 of taxable sales and $20,000 of GST-free groceries reports G1 of $100,000 if stated inclusive, 1A of $7,272.73, and nothing extra for the groceries. Leave the $20,000 out and G1 understates the quarter by a fifth; treat it as taxable and 1A is overstated by $1,818.18 of GST you never collected. The two mistakes pull in opposite directions, which is why both are common.
Which reporting method am I on?
Simpler BAS if your GST turnover is under $10,000,000, which is the default and covers most small businesses. Full reporting at $10,000,000 or more, which adds G2 export sales, G3 other GST-free sales, G10 capital purchases and G11 non-capital purchases. There is also a GST instalment method for businesses under the threshold that pay quarterly instalments and report annually, which adds 1H.
Why do I keep seeing $10 million and $20 million?
Because they are different rules that happen to sit next to each other, and mixing them up is easy. $20,000,000 is the line between reporting quarterly and having to report monthly — that is about how often. $10,000,000 is the line between Simpler BAS and full reporting — that is about how much detail. And $10,000,000 appears a third time as the turnover cap for the December monthly due-date concession. Three thresholds, two of them the same number, deciding three unrelated things.
What this calculator does not do
It is the GST section only. Your BAS may also carry PAYG withholding, PAYG instalments, FBT instalments, luxury car tax, wine equalisation tax and fuel tax credits, none of which are here. It also cannot classify your transactions: whether a particular sale is taxable, GST-free or input taxed depends on what it is, and the ATO’s own bookkeeping guide runs to dozens of transaction types and still tells you to seek advice. Give it correct totals and it will do the arithmetic correctly.

Sources

Primary sources for the BAS labels
What it decidesSourceUpdated
The Simpler BAS, instalment and full reporting label sets, and the $10 million line between themATO — GST reporting methods (QC48878)2021-04-15
That G1 may be stated inclusive or exclusive of GST, and that GST-free sales go at G1ATO — Simpler BAS GST bookkeeping guide2025-05-01
GST at 10%, the 1/11th rule and the roundingGST Act ss 9-70, 9-75, 9-902026-01-01