BAS Calculator Australia
Your quarterly GST position in seconds — Fin works out 1A, 1B and the net amount payable (or refundable), with the method shown.
Estimated amount payable this BAS
$500.00
- 1A — GST on sales (taxable sales ÷ 11)
- $1,000.00
- 1B — GST credits (purchases ÷ 11)
- −$500.00
- Net GST for the quarter
- $500.00
Figures above keep the cents; the ATO form uses whole dollars, so drop the cents when you lodge. Assumes all purchases entered are creditable and you account on a cash basis. Indicative only — general information, not tax advice.
How the BAS GST section works
The GST part of a quarterly BAS comes down to two numbers. 1A is the GST you collected: your GST-inclusive taxable sales divided by 11. 1B is the GST you can claim back: your GST-inclusive creditable business purchases divided by 11. The net GST is 1A minus 1B — positive is payable to the ATO, negative is a refund. If you pay PAYG instalments, that amount is added to the same statement.
| You want | Do this | Example |
|---|---|---|
| GST on sales (1A) | taxable sales ÷ 11 | $11,000 → $1,000 |
| GST credits (1B) | purchases ÷ 11 | $5,500 → $500 |
| Net GST | 1A − 1B | $1,000 − $500 = $500 |
General information, not tax advice. Fuel tax credits, wine equalisation, luxury car tax and GST-instalment methods aren’t modelled — confirm your BAS with the ATO or your accountant.
BAS — common questions
How do I calculate my BAS?
Take your GST-inclusive taxable sales for the quarter and divide by 11 — that is your 1A (GST on sales). Divide your GST-inclusive creditable business purchases by 11 — that is your 1B (GST credits). Your net GST is 1A minus 1B: positive means you pay the ATO, negative means a refund. Add any PAYG instalment to get the total BAS position.
What are 1A and 1B on the BAS?
1A is the GST you collected on sales; 1B is the GST credits you can claim back on business purchases. Both are one-eleventh of the GST-inclusive amounts, because GST is 10% of the pre-GST price.
When is the BAS due each quarter?
Standard quarterly due dates are 28 October (Jul–Sep quarter), 28 February (Oct–Dec), 28 April (Jan–Mar) and 28 July (Apr–Jun). Lodging online or through a registered agent can extend some of these — check your ATO account for your exact dates.
Do I need to lodge a BAS if I had no activity?
Yes — if you are registered for GST you lodge every period, even a nil BAS. Lodging nil on time keeps your account clean and avoids follow-up.
Cash or accruals — which figures go in?
On a cash basis you report GST in the quarter you were actually paid (most small businesses); on accruals you report when you invoice. This calculator assumes cash-basis figures — use whichever basis your GST registration uses.
Did you know?
Australia's GST has been frozen at 10% for over 25 years, partly because changing the rate legally requires the unanimous agreement of every state and territory plus both houses of federal Parliament.
Treasury states plainly that 'legislation requires that changes to the GST base or rate require unanimous agreement by all State and Territory governments, as well as both houses of the Australian Parliament' — a political straitjacket flowing from the 1999 Intergovernmental Agreement that has kept the rate untouched since 1 July 2000.
Source: Australian Treasury — Tax White Paper, At a glance ↗Whether a frozen meal is taxed can hinge on a judge deciding what counts as a 'prepared meal' by common experience — and Simplot (maker of Birds Eye products) lost that argument in 2023.
In Simplot Australia v Commissioner of Taxation [2023] FCA 1115 the Federal Court ruled frozen vegetable-, rice- and pasta-based products were taxable 'prepared meals' or 'combination foods', applying 'common experience and common sense' about what an everyday meal is rather than the maker's own marketing.
Source: Grant Thornton — GST and food: Federal Court challenges the concept of a prepared meal ↗Walk into BAS time already done
Connect your bank and Fin tracks the GST on every transaction through the quarter — so 1A and 1B are ready before you are. Free to start, no card needed.
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