What goes on a sole trader’s BAS
A business activity statement reports two things for most GST-registered sole traders:
- GST. The GST in your sales (label 1A) less the GST in your business purchases (label 1B). With 10% GST, the GST inside a GST-inclusive amount is one eleventh of it.
- PAYG instalments. An advance on next year’s income tax, if the ATO has put you into the system. Either a rate the ATO gives you, applied to your instalment income (sales excluding GST), or a fixed amount it calculates.
GST on sales = sales ÷ 11 · GST credits = purchases ÷ 11
PAYG instalment = (sales − GST) × instalment rate
A worked example
With the figures loaded above, for July to September 2026 you invoiced $33,000 including GST and spent $5,500 including GST on business purchases. Your instalment rate is 8%.
- GST on sales is $33,000 ÷ 11 = $3,000.
- GST credits are $5,500 ÷ 11 = $500, so net GST is $2,500.
- Instalment income is $33,000 − $3,000 = $30,000, and 8% of it is a $2,400 PAYG instalment.
- The BAS totals $4,900, due 28 October 2026. That is 14.8% of everything you received in the quarter.
- Spread over the 13 weeks of the quarter, that is $376.92 a week.
Quarterly due dates
For a quarterly BAS you lodge yourself, the usual due dates are 28 October (July–September), 28 February (October–December), 28 April (January–March) and 28 July (April–June). If you lodge through a registered tax or BAS agent, later dates often apply. When a due date falls on a weekend or public holiday, you can lodge and pay on the next business day.
The GST was never yours
The single most useful habit is to move one eleventh of every GST-inclusive payment into a separate account the day it arrives, and the PAYG percentage of the rest with it. GST that sits in the everyday account for three months gets spent, and the BAS then becomes a cash-flow problem instead of a form.
- Not everything has GST. Bank fees, most residential rent, wages and many basic foods carry no GST, so there is no credit to claim on them.
- Private use. Only the business portion of a mixed-use purchase, such as a phone or a car, is creditable.
- PAYG is not the whole tax bill. Instalments are based on an earlier year. If income has risen, the final bill can still be larger. The Australian sole trader set-aside guide covers the income tax side, including the 31 October lodgement deadline.
Pricing your work so the GST and tax are covered starts with the contractor day rate calculator.