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BAS calculator
Type your sales, purchases, PAYG withholding and instalment for the period. You get every label to fill in, in whole dollars, and what you pay or get back at 9. It follows the ATO’s own GST calculation worksheet and BAS instructions.
How do you report GST?
PAYG tax withheld (wages and no-ABN payments)
Gross payments you withhold from. Not added into the total.
47% of payments to suppliers who didn't quote an ABN.
Investment income without a TFN, payments to foreign residents and similar.
Large withholders complete only W1. Working out W4? Use the no-ABN withholding calculator.
PAYG income tax instalment
Other amounts on your statement (optional)
Any other amount your statement adds to 8A, such as wine equalisation tax, luxury car tax or an FBT instalment.
Any other credit your statement adds to 8B, such as fuel tax credits.
Type your figures above to see each label and what you pay or get back at 9.
Nothing you type leaves your browser. It applies the ATO’s published BAS instructions to the figures you enter; it isn’t tax advice, and your own records decide what goes in each label.
How the BAS adds up
A business activity statement is a few separate calculations that only meet in the summary at the end. From the ATO’s instructions for completing your BAS (last updated 14 September 2026): round down to whole dollars, and don’t report negative figures or symbols.
- GST on sales (1A). With the worksheet method, every amount includes GST (Step 1: Sales). G5 = G2 + G3 + G4, G6 = G1 minus G5, G8 = G6 + G7, and G9 = G8 divided by 11, which goes to 1A (Step 2).
- GST on purchases (1B). G12 = G10 + G11, G16 = G13 + G14 + G15, G17 = G12 minus G16, G19 = G17 + G18, and G20 = G19 divided by 11, which goes to 1B (Step 4). G14 includes purchases made from an entity not registered for GST.
- PAYG tax withheld (4). W5 = W2 + W4 + W3 (not W1), copied to 4 (PAYG withholding labels, last updated 1 May 2025).
- PAYG income tax instalment (5A). T7, or a varied T9, or T1 × T2 = T11 (PAYG instalments: how to complete your activity statement).
- Summary. 8A = 1A + 4 + 5A, 8B = 1B + 5B, and 9 is the difference: payable if 8A is bigger, refundable if 8B is (Step 5: Summary, last updated 9 September 2026).
Most businesses with a GST turnover under $10 million use Simpler BAS and report only G1, 1A and 1B. The ATO also publishes its own GST calculation worksheet (NAT 5107) as a fillable PDF.
The figure most worth checking: 1B
1B is a claim. It should only include GST you were charged by suppliers who were registered for GST when they invoiced you; anything bought from a supplier who wasn’t belongs at G14. A supplier list from Xero, MYOB or QuickBooks can be checked in one go with the bulk ABN and GST check, which looks at each bill’s invoice date (the first 25 rows are free). For one supplier, use the GST registration check. The guide to checking a quarter’s bills before the BAS walks through it.
Common questions
How do I calculate the GST on my BAS?
With the ATO's calculation worksheet: take total sales including GST (G1), subtract the GST-free, export and input-taxed sales, add any increasing adjustments, and divide by 11. That's 1A, GST on sales. For purchases, take total purchases including GST, subtract purchases with no GST in the price, purchases for making input-taxed sales and the private or non-deductible share, add any decreasing adjustments, and divide by 11. That's 1B, GST on purchases. If your software already reports GST amounts, you can use the accounts method and take 1A and 1B straight from your records.
What do I report with Simpler BAS?
Only G1 Total sales, 1A GST on sales and 1B GST on purchases. Simpler BAS is the default for businesses with a GST turnover under $10 million, and you don't report G2, G3, G10 or G11.
How are 8A, 8B and 9 worked out?
8A adds up what you owe: 1A GST on sales, 4 PAYG tax withheld (copied from W5) and 5A PAYG income tax instalment, plus any other amounts your statement asks for. 8B adds up what the ATO owes you: 1B GST on purchases and 5B (a credit from varying your instalment), plus any other credits. If 8A is more than 8B, the difference at 9 is payable to the ATO; if 8B is more, it's refundable to you (or offset against other tax debts).
Do I round the BAS figures?
The ATO asks for whole dollars, with the cents dropped (rounded down), and no negative figures or symbols. This calculator works to the cent, then drops the cents from each label.
What goes at W1, W2, W4 and W5?
W1 is the gross salary, wages and other payments you withhold from. W2 is the tax you withheld from those payments. W4 is the amount withheld from suppliers who didn't quote an ABN (47%). W3 is other withholding. W5 is W2 + W4 + W3 (W1 isn't added in), and W5 is copied to label 4 in the summary.
How do I work out my PAYG instalment (5A)?
Under option 1 you pay the instalment amount the ATO printed at T7, or a varied amount at T9 with a reason code at T4. A negative varied amount is entered as 0 and the credit is claimed at 5B. Under option 2 you multiply your instalment income (T1, generally gross business and investment income excluding GST) by the instalment rate at T2, and enter the result at T11 and 5A.
Can I claim GST credits on a bill from a supplier who isn't registered for GST?
No. Purchases from an entity not registered for GST go at G14 (purchases without GST in the price), so they're taken out before 1B is worked out. If a supplier charged GST but wasn't registered on the invoice date, there's no GST credit to claim. Check the supplier on the register before you lodge.
Do I lodge the worksheet?
No. The worksheet lines (G4 to G9 and G12 to G20) aren't reported on the BAS. The ATO recommends filing the worksheet with a copy of the BAS it relates to.
Is this tax advice?
No. It applies the ATO's published BAS instructions to the figures you type, and nothing is sent anywhere. What belongs in each label depends on your records; a registered tax or BAS agent can confirm it.
More: BAS due dates 2026–27 · late BAS penalty calculator · GST calculator · no-ABN withholding (W4) calculator · GST registration check · check a supplier list