How is a BAS calculated?

For the GST part, take the GST you collected on sales (1A) and subtract the GST you paid on business purchases (1B). If 1A is bigger you pay the difference. If 1B is bigger you get a refund.

What are G1, 1A and 1B on a BAS?

G1 is your total sales, including GST-free sales. 1A is the GST on your sales. 1B is the GST included in the price of your purchases, which you claim back as a credit.

Does this give me a BAS I can lodge?

No. It estimates the GST part of a simpler BAS (G1, 1A and 1B). Your own BAS may also include PAYG withholding or instalments, and you lodge it through ATO online services or a registered agent.

BAS Calculator Australia

Work out the GST part of your BAS. Enter your sales and purchases for the period and you get G1 (total sales), 1A (GST on sales) and 1B (GST on purchases), plus whether you pay or get a refund.

GST on your BAS

Estimate only. This is not a BAS you can lodge. Enter amounts for one BAS period.

Sales that include GST

GST-free sales (optional)

Business purchases that include GST

How to calculate your BAS

Simpler BAS is the default for businesses with a GST turnover under $10 million, and it reports three GST figures. G1 is your total sales. 1A is the GST you charged on those sales. 1B is the GST you paid on business purchases.

Subtract 1B from 1A. A positive answer is what you pay the ATO. A negative answer is a refund.

Try it with these figures

A sole trader with $16,500 of sales and $6,600 of purchases, both including GST.

G1 Total sales	$16,500.00
1A GST on sales ($16,500 ÷ 11)	$1,500.00
1B GST on purchases ($6,600 ÷ 11)	$600.00

GST to pay (1A minus 1B)	$900.00

What this calculator leaves out

It only covers the GST labels, and it is for Simpler BAS. If your GST turnover is $10 million or more you use full reporting, which has more labels. Enter only purchases that have GST in the price and that you can claim credits on. If you have staff you may also report PAYG withholding, and you may pay PAYG instalments.

Use the same reporting period for sales and purchases.

Skip the adding up

Instant Receipts reads the GST on every receipt, matches it to your bank transactions and shows your BAS figures for the period. You check them, then lodge through the ATO as usual.

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BAS calculator: frequently asked questions

For the GST part, take the GST you collected on sales (1A) and subtract the GST you paid on business purchases (1B). If 1A is bigger you pay the difference. If 1B is bigger you get a refund.
G1 is your total sales, including GST-free sales. You can report it with or without GST as long as you say which on the form. 1A is the GST on your sales. 1B is the GST included in the price of your purchases, which you claim back as a credit. You do not report your total purchases.
Your sales and your business purchases for one BAS period, with the GST included. GST-free sales go in their own box. They count towards G1 but add no GST.
No. It estimates the GST part of a simpler BAS (G1, 1A and 1B). Your own BAS may also include PAYG withholding or instalments, and you lodge it through ATO online services or a registered agent.

Want your BAS figures worked out for you?

Scan your receipts, then connect your bank or upload a statement, and Instant Receipts builds the BAS figures for your period. Check them, then lodge with the ATO.

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