Guides / BAS
What you need for your BAS
The figures that matter, and how to keep them tidy through the year instead of scrambling the week it's due.
What a BAS is
A Business Activity Statement (BAS) is how a GST-registered business reports GST — and often PAYG instalments and withholding — to the ATO. If you're registered for GST, you'll lodge one regularly, most commonly quarterly, though some businesses lodge monthly or annually depending on turnover and how they've chosen to report.
Quarterly BAS is generally due 28 days after the end of the quarter (with a little extra time for the December quarter). Lodging through a registered tax or BAS agent can also extend your due date — worth asking your accountant about.
The three figures that do the work
Underneath the BAS form, GST reporting comes down to three numbers:
G1 — Total sales
All the sales you made in the period, GST-inclusive.
1A — GST on sales
The GST you collected from customers — the amount you owe the ATO from your sales side.
1B — GST on purchases
The GST you paid on business purchases — your GST credits, which reduce what you owe.
Your net GST is simply 1A minus 1B. If it's positive, you pay the ATO that amount; if it's negative, you get a refund.
Cash basis vs accrual
Most small businesses (turnover under $10 million) can choose to report GST on a cash basis — meaning G1 and 1A count sales when the money actually lands, not when you issue the invoice, and 1B counts purchases when you actually pay for them. This tends to be simpler and matches how the money genuinely moves through your bank account, which is why it's the basis most sole traders use.
Preparing for BAS without the scramble
- Issue a proper tax invoice for every sale — see our tax invoice guide.
- Record expenses as they happen, with the correct GST treatment and a receipt kept.
- Reconcile your bank statement regularly so nothing slips through unrecorded.
- Keep GST-free and input-taxed sales/purchases correctly tagged — they shouldn't inflate 1A or 1B.
- Set aside the GST you collect rather than treating it as income — it isn't yours to spend.
Your BAS figures, already sorted
Because Billaroo tracks GST correctly on every invoice and expense as you go, your GST/BAS summary — G1, 1A, 1B and the net figure — is ready the moment you need it, calculated from the same records your accountant can export in one click.
This guide is general information, not tax advice — lodgment cycles, due dates and thresholds can change, so confirm your own obligations with the ATO or a registered tax or BAS agent.