BAS Calculator Australia
Estimate an Australian BAS payment or refund from taxable transactions, or combine your actual 1A, 1B, W5, 5A and 5B labels. Whole-dollar ATO-aligned breakdown.
Only standard 10% taxable sales — not all sales reported at G1.
Only the portion eligible for a full GST credit.
Exclude GST-free, private and non-creditable purchases.
W2 + W3 + W4. Do not enter W1 gross wages here.
Enter the payable instalment at 5A — not T1 instalment income.
Optional credit from a PAYG instalment variation.
Enter your BAS figures to calculate the payment or refund.
Business calculators: Company tax calculator, Franking credits calculator, Trust distribution tax calculator, Division 7A calculator, Sole trader tax calculator
Estimate first, then confirm against your BAS
Estimate from totals
For simple businesses with standard 10% taxable sales and purchases eligible for full GST credits. It estimates 1A and 1B by extracting one-eleventh, then rounds each BAS label down to a whole dollar.
Use BAS labels
For a more reliable payment summary, copy 1A, 1B, W5, 5A and 5B from your accounting records or issued activity statement. The calculator combines them without treating gross wages or instalment income as tax.
How the BAS summary is calculated
Net GST = 1A GST on sales − 1B GST on purchases
Net PAYG instalment = 5A instalment − 5B variation credit
Estimated BAS position = Net GST + W5 withholding + Net PAYG instalment
G1 total sales, W1 gross payments and T1 instalment income can still be required on your personalised BAS, but they are not added directly to this payment calculation.
The labels that affect this estimate
1A — GST on sales
GST payable on taxable sales for the period, including relevant increasing adjustments.
1B — GST on purchases
GST credits you are entitled to claim, including relevant decreasing adjustments.
W5 — Total amounts withheld
The total of W2, W3 and W4. W1 is gross payments and must not be substituted for W5.
5A — PAYG income tax instalment
The instalment amount payable, either advised by the ATO or calculated using the applicable option.
5B — PAYG instalment variation credit
An eligible credit from varying a PAYG instalment. Enter it as a positive credit amount; it is subtracted in the summary.
Standard BAS lodgment dates
| Cycle | Period | Standard due date |
|---|---|---|
| Quarterly | July – September | 28 October |
| Quarterly | October – December | 28 February |
| Quarterly | January – March | 28 April |
| Quarterly | April – June | 28 July |
| Monthly | Each month | 21st of following month |
| Annual GST return | Financial year | With income tax return; otherwise generally 28 February |
Check the issued statement: it carries the due date that applies to you. Eligible online quarterly lodgers may receive an extra two weeks for quarters 1, 3 and 4; registered agents may have different concessions. Quarter 2 already includes an extension.
Simple transaction estimate
A retailer has $55,000 total sales, of which $5,000 is GST-free. The estimate therefore uses $50,000 of standard taxable sales, not the full G1 amount.
Estimated 1A: $50,000 ÷ 11 = $4,545 whole dollars
Estimated 1B: ($11,000 + $22,000 fully creditable purchases) ÷ 11 = $3,000
Net GST: $4,545 − $3,000 = $1,545
Estimated BAS: $1,545 + $4,500 W5 + $1,200 at 5A = $7,245 owing
The business should replace estimated 1A and 1B with its actual accounting-system or BAS figures before lodging, particularly if it has mixed supplies, adjustments or partly creditable purchases.
What is a Business Activity Statement (BAS)?
Why doesn't this calculator divide G1, G10 and G11 by 11?
Which PAYG withholding figure goes into the BAS total?
Should I enter T1 or 5A for PAYG instalments?
When is my BAS due?
Do I need to lodge if every amount is zero?
Does a negative result guarantee an immediate refund?
What happens if I lodge or pay late?
Tax Accuracy & Sources
Planning estimate for a single BAS period. Transaction mode assumes standard 10% taxable sales and purchases eligible for full GST credits; label mode combines entered summary labels. It does not calculate adjustments, mixed or input-taxed supplies, partial credits, WET, LCT, fuel tax credits, FBT, other activity-statement labels, penalties or ATO account offsets.