This estimator turns your sales and purchases into the key BAS figures: G1 (total sales), 1A (GST on sales), 1B (GST on purchases) and your net GST — the amount you pay the ATO, or the refund due to you. Enter your figures above, then use the print button for a summary you can keep with your records.
Already know your GST is due? Work backwards from a total with the Reverse GST Calculator, or check whether you need to be registered at all with the Registration Threshold Checker.
How the BAS labels fit together
The estimator follows the same path as the GST section of your activity statement:
- G1 — Total sales. Everything you sold for the period, including GST, GST-free and input-taxed sales.
- Taxable sales = G1 minus your GST-free sales and input-taxed sales.
- 1A — GST on sales = taxable sales ÷ 11.
- G10 and G11 — Purchases. Your capital (G10) and non-capital (G11) purchases, including GST.
- 1B — GST on purchases = your GST-inclusive purchases ÷ 11.
- Net GST = 1A − 1B. If 1A is larger you pay the difference; if 1B is larger you receive a refund.
Worked example
A business has $110,000 in total sales for the quarter, of which $11,000 is GST-free. Its taxable sales are $99,000, so 1A = $99,000 ÷ 11 = $9,000. It made $11,000 of capital purchases and $22,000 of non-capital purchases — $33,000 in total — so 1B = $33,000 ÷ 11 = $3,000. The net GST is $9,000 − $3,000 = $6,000 payable to the ATO.
Which sales are GST-free or input-taxed?
GST-free sales include exports, most basic food, and many health and education services. Input-taxed sales include residential rent and most financial supplies. Both are part of your total sales (G1) but carry no GST, so they are subtracted before working out 1A.
Capital vs non-capital purchases
Capital purchases (G10) are one-off purchases of equipment, tools or vehicles. Non-capital purchases (G11) are your everyday running costs — stock, rent, supplies and services. Both feed into 1B, so the split does not change your GST credit; it is reported separately for the ATO’s information.
A note on Simpler BAS and accounting method
Most small businesses (GST turnover under $10 million) use Simpler BAS and only report G1, 1A and 1B — which is exactly what this tool estimates. Whether you include a sale or purchase this period also depends on whether you account for GST on a cash or accruals basis.
Common mistakes
- Claiming GST on GST-free purchases. Bank fees, most basic food and wages carry no GST — do not include them in your purchase figures for 1B.
- Forgetting to subtract GST-free and input-taxed sales. They belong in G1 but not in the taxable sales that drive 1A.
- Mixing up capital and non-capital. It will not change your net GST, but it should still be reported at the right label.
- Reporting cents. The actual BAS is completed in whole dollars.
Frequently asked questions
How do I work out GST on sales for my BAS?
Take your total sales, subtract any GST-free and input-taxed sales to get taxable sales, then divide by 11. That is label 1A.
What is the difference between 1A and 1B?
1A is the GST you collected on sales. 1B is the GST credits you can claim on business purchases. You pay the ATO the difference (1A minus 1B), or receive it as a refund if 1B is larger.
Do I include GST-free sales in G1?
Yes. G1 is your total sales including GST-free and input-taxed sales. They are only excluded when working out the taxable sales behind 1A.
Is this the same as lodging my BAS?
No. This is an estimate to help you plan and check your figures. Lodge your actual BAS through the ATO’s Online services or a registered agent.