GST calculation worksheet for BAS (G1 to G20 calculator)
An online version of the ATO's GST calculation worksheet for BAS (NAT 5107). Enter your GST-inclusive sales and purchases and it works out G5 to G9 (GST on sales, for 1A) and G12 to G20 (GST on purchases, for 1B). It also shows the net GST you owe or get back, and the whole-dollar amounts to copy onto your BAS.
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WorksheetWhat goes at each labelExampleFAQ
What goes at each label
- G1: all sales, including GST, GST-free and input-taxed sales. With the worksheet method, every amount includes GST.
- G2 / G3 / G4: the parts of G1 that are exports, other GST-free sales, and input-taxed sales (such as residential rent or financial supplies). G4 isn't reported on the BAS.
- G7: increasing adjustments. G9 = G8 ÷ 11 goes to 1A.
- G10 / G11: capital and non-capital purchases, including GST.
- G13 / G14 / G15: the parts of G10 and G11 you can't claim a GST credit for: purchases for input-taxed sales, purchases with no GST in the price, and private or non-deductible purchases. They aren't reported on the BAS.
- G18: decreasing adjustments. G20 = G19 ÷ 11 goes to 1B.
On the BAS itself, round down to whole dollars (don't show cents), and don't report negative figures.
Example
A quarter with $55,000 of sales (G1), including $5,000 of GST-free sales (G3). Purchases are $11,000 of equipment (G10) and $22,000 of other purchases (G11), of which $2,200 had no GST (G14) and $1,100 was private (G15).
- G6 = $55,000 − $5,000 = $50,000, so G9 = $50,000 ÷ 11 = $4,545.45 → 1A $4,545.
- G12 = $33,000, G16 = $3,300, G17 = $29,700, so G20 = $29,700 ÷ 11 = $2,700 → 1B $2,700.
- Net GST payable: $4,545 − $2,700 = $1,845.
FAQ
How do I use the GST calculation worksheet for BAS?
Enter total sales including GST at G1, then the GST-free and input-taxed parts at G2, G3 and G4. G6 is G1 minus their total, plus adjustments at G7 gives G8, and G8 divided by 11 is your GST on sales for 1A. Purchases work the same way from G10 and G11 down to G20, which goes to 1B.
Do I include GST in the amounts on the worksheet?
Yes. With the calculation worksheet method, every amount includes GST. Only the accounts method lets you choose GST-exclusive amounts at G1.
Which worksheet labels go on my BAS?
G1, G2, G3, G10 and G11 go on the BAS, with G9 at 1A and G20 at 1B. G4 to G8 and G12 to G19 are worksheet-only, but keep the worksheet with a copy of the BAS.
Do I round BAS amounts?
Yes. The ATO says to round down to whole dollars and not show cents. It also says not to report negative figures or use symbols like plus, minus or dollar signs.
What is the difference between 1A and 1B?
1A is the GST on your sales that you owe the ATO. 1B is the GST credits on your purchases that the ATO owes you. If 1A is more than 1B you pay the difference. If 1B is more, you get a refund.
Sources (checked 17 Oct 2026): ATO GST calculation worksheet for BAS (NAT 5107); ATO Step 2: Calculating sales using the calculation worksheet; ATO Step 4: Calculating purchases using the calculation worksheet; ATO Instructions for completing your BAS.
General information, not tax advice. This follows the calculation worksheet method only. It doesn't apply to the accounts method, GST instalments (Option 3) or Simpler BAS. Check the ATO's rules for less common transactions.