# How much do I owe on my BAS?

Works out the GST on sales (1A), GST credits on purchases (1B), PAYG withholding and PAYG instalment for an Australian business activity statement, and the net amount to pay or get back.

- Page: https://www.acalculator.org/finance/bas-calculator
- JSON spec: https://www.acalculator.org/finance/bas-calculator.json
- Version: e42ba6d46f3d

## Default answer

Example with the default inputs (Total sales (G1) $55,000.00, GST-free sales and exports (G2 + G3) $0.00, Purchases (G10 + G11) $22,000.00, Purchases with no GST in them $0.00, PAYG tax withheld (W2) $0.00, PAYG instalment income (T1) $0.00, PAYG instalment rate (T2) 0%): Net amount for this BAS: $3,000.00. You pay the ATO.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| g1 | Total sales (G1) | All sales in the period, including GST, as on label G1. |
| g3 | GST-free sales and exports (G2 + G3) | Export sales (G2) and other GST-free sales (G3) included in G1; no GST is due on them. |
| g11 | Purchases (G10 + G11) | Capital purchases (G10) and other purchases (G11), including GST. |
| nogst | Purchases with no GST in them | The part of the purchases that had no GST: GST-free or input-taxed items, wages, and private use. |
| w2 | PAYG tax withheld (W2) | Tax withheld from wages and other payments in the period (label W2). |
| t1 | PAYG instalment income (T1) | Instalment income for the quarter, if you pay PAYG instalments by rate (label T1). |
| t2 | PAYG instalment rate (T2) | The instalment rate the ATO gave you (label T2). |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| net | Net amount | GST on sales plus PAYG withheld and instalment, less GST credits. Negative means a refund. |
| direction | Pay or refund | Whether you pay the ATO or the ATO pays you. |
| gstOnSales | GST on sales (1A) | One eleventh of the taxable sales. |
| gstCredits | GST credits (1B) | One eleventh of purchases that included GST. |
| netGst | Net GST | 1A less 1B. Negative means a GST refund. |
| instalment | PAYG instalment (T11) | Instalment income times the instalment rate. |
| withheldOut | PAYG withheld (W2) | The tax withheld, as typed. |

## Method

1A = (G1 − GST-free sales) ÷ 11; 1B = (purchases − purchases with no GST) ÷ 11; T11 = T1 × T2 ÷ 100; net = 1A − 1B + W2 + T11. A negative net is a refund.

## Assumptions

- GST is 10%, so the GST in a GST-inclusive amount is one eleventh of it (ATO).
- Sales and purchases are typed including GST, as on the BAS labels G1, G10 and G11.
- The page does not apply adjustments (1G, 7), fuel tax credits, wine equalisation tax, luxury car tax, or a PAYG instalment varied from the ATO amount. It is an estimate, not tax advice.

## Worked examples

1. g1 = $55,000.00, g11 = $22,000.00 gives gstOnSales = $5,000.00, gstCredits = $2,000.00, netGst = $3,000.00, net = $3,000.00, direction = You pay the ATO. Source: ATO, Quarterly GST reporting, https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/when-and-how-to-report-and-pay-gst/quarterly-gst-reporting.
2. g1 = $33,000.00, g3 = $5,500.00, g11 = $13,200.00, nogst = $2,200.00, w2 = $4,100.00, t1 = $30,000.00, t2 = 4.5% gives gstOnSales = $2,500.00, gstCredits = $1,000.00, netGst = $1,500.00, instalment = $1,350.00, net = $6,950.00. Source: ATO, Quarterly GST reporting, https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/when-and-how-to-report-and-pay-gst/quarterly-gst-reporting.
3. g1 = $11,000.00, g11 = $66,000.00 gives netGst = -$5,000.00, net = -$5,000.00, direction = The ATO refunds you. Source: ATO, Quarterly GST reporting, https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/when-and-how-to-report-and-pay-gst/quarterly-gst-reporting.
4. g1 = $100.00 gives gstOnSales = $9.09, net = $9.09. Source: ATO, Quarterly GST reporting, https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/when-and-how-to-report-and-pay-gst/quarterly-gst-reporting.

## FAQ

### How do I calculate GST for my BAS?

GST is 10%, so the GST inside a GST-inclusive price is one eleventh of it. GST on sales (1A) is your taxable sales divided by 11; GST credits (1B) are your purchases that included GST divided by 11. Net GST is 1A minus 1B.

### What goes in G1, G2 and G3?

G1 is all your sales in the period, including GST. G2 is export sales and G3 is other GST-free sales; both are part of G1 but carry no GST, so they are taken out before dividing by 11.

### What are G10 and G11?

G10 is capital purchases (equipment, vehicles) and G11 is all other purchases, both including GST. Only purchases that had GST in them give a GST credit; leave out wages, bank fees, and GST-free items.

### What are W1 and W2?

W1 is the total of wages and other payments you made, and W2 is the tax you withheld from them. W2 is added to the amount you owe on the BAS.

### How is the PAYG instalment worked out?

If you pay by rate, the instalment is your instalment income (T1) times the rate the ATO gave you (T2). For example, $30,000 at 4.5% is $1,350.

### What if the net amount is negative?

A negative amount means your GST credits are larger than the GST and PAYG you owe, so the ATO refunds the difference. This is common in a quarter with a big purchase.

### Do I need to report every label?

Businesses with GST turnover under $10 million use Simpler BAS and report only G1, 1A and 1B for GST. Larger businesses use full reporting. The arithmetic for 1A and 1B is the same.

## Sources

- ATO, How Australian GST works: the rate is 10% and GST is one eleventh of the price (updated 11 September 2025, retrieved 2026-10-05). https://www.ato.gov.au/businesses-and-organisations/international-tax-for-business/gst-for-non-resident-businesses/how-australian-gst-works
- ATO, Quarterly GST reporting: labels G1, G2, G3, G10, G11, 1A and 1B, and Simpler BAS (retrieved 2026-10-05). https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/when-and-how-to-report-and-pay-gst/quarterly-gst-reporting
- ATO, PAYG withholding on the BAS: labels W1 and W2 (retrieved 2026-10-05). https://www.ato.gov.au/businesses-and-organisations/preparing-lodging-and-paying/business-activity-statements-bas/pay-as-you-go-payg-withholding
- ATO, PAYG instalments: how to complete your activity statement, labels T1, T2 and 5A (retrieved 2026-10-05). https://www.ato.gov.au/forms-and-instructions/payg-instalments-how-to-complete-your-activity-statement