The September-quarter BAS is due on 28 October, and the GST and PAYG it will collect from you have been quietly accumulating in your accounts since 1 July. The mid-quarter cash check is one hour, roughly now, to work out what that bill will be before it falls due — while you still have two months to set the money aside instead of finding it in a panic on lodgement day.
Why the BAS surprise happens at all
GST you collect on sales isn't your money; it just sits in the same bank account as money that is. Same with the PAYG you withhold from wages. Across a quarter that pooled cash can look like healthy working capital, and it is very easy to spend. Then the BAS lands, asks for a quarter's worth back, and a business that felt fine discovers it is short. The surprise is almost never a profitability problem. It is a timing problem, and timing problems are fixable when you see them early.
The one-hour check
You do not need a forecast, just a rough tally of where the quarter stands so far. Four numbers:
First, GST collected on sales to date minus GST paid on purchases to date — that is your rough net GST. Second, the PAYG you have withheld from wages so far this quarter. Third, any PAYG instalment you are liable for. Add those together for a ballpark of what 28 October will ask for. Fourth, the cash you have actually earmarked against it. The gap between the two is the number that matters, and it is far better to meet it in late August than in late October.
What to do with the number
If you are short, start moving money into a separate tax account weekly from now — the simplest system in small business finance is a second bank account that GST and PAYG go into and never come out of except to pay the ATO. Chase your overdue debtors now, so the cash you are counting on in October is real rather than hopeful. And if the check shows you are comfortably covered, you have bought genuine peace of mind for the price of an hour.
Make it a quarterly rhythm
The real win is turning this from a one-off into a habit: a mid-quarter cash check in mid-February, mid-May, mid-August and mid-November. Do that and every BAS becomes a confirmation of a number you already knew, not a discovery. Our cash flow gap calculator can help you pressure-test the timing, and the Finance Hub sets out how the quarterly cycle fits the rest of your compliance calendar.
FAQ
Isn't this my bookkeeper's job?
Your bookkeeper produces the numbers; the decision about whether to set cash aside is yours. The point of the check is to move that decision two months earlier, when you still have options.
I lodge through a BAS agent and get extra time. Should I still bother?
Yes. A later due date changes when you pay, not how much — and the extra weeks are wasted if the cash was spent because nobody looked until the deadline.
I'm on cash-basis GST. Does the check still work?
It works the same way; you just tally GST on payments received and made rather than on invoices. The principle — know the number before it's due — is identical.
Sources: Australian Taxation Office, Due dates for lodging and paying your BAS. Current as at 24 July 2026. General information, not advice.
Want a clearer view of what's coming? Our free Business Health Check looks at your cash rhythm and compliance calendar together.
About the author
Nick Lucock
Chief Executive Officer, Valont
Nick leads Valont's day-to-day operations across Finance, People, Operations and Growth. He writes about how the work actually gets done — the processes, systems, and tools that keep Australian SMEs compliant and growing.
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