The worked quarter
| Incl. GST | GST (÷ 11) | |
|---|---|---|
| Sales (G1) | $33,000 | $3,000 → label 1A |
| Business purchases with GST | $11,000 | $1,000 → label 1B |
| Net GST payable | $2,000 |
You collected $3,000 of GST from customers and paid $1,000 of GST to suppliers, so you hand the difference — $2,000 — to the ATO. If your credits were bigger than the GST on sales (common in a quarter with a big equipment purchase), the ATO would refund you.
Cash or accrual?
Most small businesses (turnover under $10 million) can use the cash basis: you report GST in the quarter you are paid and claim credits in the quarter you pay. On the accrual basis you report when you issue or receive the invoice, even if it is unpaid.
Common mistakes to avoid
- Claiming credits on GST-free purchases (bank fees, most insurance stamp duty, wages, basic food).
- Claiming the full GST on a mixed-use item such as a phone — claim only the business share.
- Forgetting that your sales figure on G1 includes GST, while 1A is only the GST.
- Missing tax invoices for purchases over $82.50.
Due dates
Quarterly BAS is generally due on 28 October, 28 February, 28 April and 28 July (the December quarter is due 28 February). Lodging through a registered agent can give extra time.
The calculator above is pre-filled with this quarter. Change the sales and purchases to your own figures to get your estimate.
Paying and planning
Pay using the BPAY or EFT details on your BAS, quoting your payment reference number. If you can’t pay in full, lodge on time anyway and set up a payment plan online — the failure-to-lodge penalty is separate from interest on late payment. A simple habit helps: move one-eleventh of every GST-inclusive sale into a separate savings account as you are paid, so the money is there when the BAS is due.
Remember the BAS also covers PAYG withholding for employees and, for some, PAYG instalments on income tax. This page only covers the GST labels. If your figures change a lot from quarter to quarter, it is worth reviewing them with a registered BAS agent.
Key GST figures (checked 5 November 2026)
| Item | Figure |
|---|---|
| GST rate | 10% |
| GST inside an inclusive price | ÷ 11 |
| Registration threshold | $75,000 GST turnover ($150,000 non-profits) |
| Tax invoice needed for credits | Purchases over $82.50 incl. GST |
| Quarterly BAS due | 28 Oct, 28 Feb, 28 Apr, 28 Jul |
FAQ
How do I calculate GST payable on my BAS?
GST on sales (sales incl. GST ÷ 11) minus GST credits on purchases (purchases incl. GST ÷ 11).
What is the GST on $33,000 of sales including GST?
$3,000. The sales before GST were $30,000.
What if my GST credits are more than the GST on sales?
The ATO refunds the difference after you lodge the BAS.
Sources (checked 5 November 2026): A New Tax System (Goods and Services Tax) Act 1999 (s 9-70 rate of 10%, s 23-15 registration turnover thresholds); ATO “Registering for GST”, “GST-free sales”, “Tax invoices” and “Business activity statements (BAS)” guidance.