BAS GST Calculator Australia (2026–27)
Calculate your quarterly Business Activity Statement (BAS) Goods and Services Tax (GST) payable under current ATO rules. Model 1A GST collected on sales vs 1B input tax credits, cash vs accruals reporting, and quarterly deadlines.
Net GST Payable to ATO
$5,091
Net amount you owe the ATO for this BAS quarter/month.
Box 1A (GST Collected on Sales)
$9,091
Box 1B (GST Credits on Purchases)
$4,000
BAS GST Reporting Box Breakdown
1. The Australian BAS GST Framework (2026–27)
The Australian Goods and Services Tax (GST) is a broad-based value-added tax of 10% governed by the A New Tax System (Goods and Services Tax) Act 1999.
Businesses registered for GST act as tax collectors for the ATO, remitting net GST (GST collected minus input tax credits) on quarterly Business Activity Statements.
2. Quarterly Sales Turnover & GST Payable Benchmarks
| Quarterly Sales (G1) | GST Collected (1A) | GST Credits (1B) | Net BAS GST Payable | Annual GST Remittance |
|---|---|---|---|---|
| $55,000 Sales ($5,000 GST) | $5,000 GST Collected | $1,500 GST Credits | $3,500 Net Payable | $14,000 / year |
| $110,000 Sales ($10,000 GST) | $10,000 GST Collected | $3,200 GST Credits | $6,800 Net Payable | $27,200 / year |
| $220,000 Sales ($20,000 GST) | $20,000 GST Collected | $7,500 GST Credits | $12,500 Net Payable | $50,000 / year |
| $550,000 Sales ($50,000 GST) | $50,000 GST Collected | $18,000 GST Credits | $32,000 Net Payable | $128,000 / year |
3. The Mathematics of 1/11th GST Calculations
Net BAS GST Liability (GST_net) for total GST-inclusive sales (S_total) and total GST-inclusive business purchases (P_total) is:
Example Calculation ($110,000 Sales, $33,000 Purchases GST-Inclusive):
- GST Collected on Sales (Item 1A): $110,000 ÷ 11 = $10,000.00.
- GST Input Tax Credits (Item 1B): $33,000 ÷ 11 = $3,000.00.
- Net BAS GST Remittance to ATO = $10,000 - $3,000 = $7,000.00 BAS payment.
4. Step-by-Step Guide to Preparing Quarterly BAS
Sum Quarterly Gross Sales (Item G1)
Calculate total gross sales and client fees (GST-inclusive) received during the 3-month BAS quarter.
Calculate Total GST Collected on Sales (Item 1A)
Divide GST-inclusive sales (G1) by 11 to derive total 10% GST collected from customers.
Itemize Business Capital & Non-Capital Purchases (G10 & G11)
Sum total business expenditure on equipment, stock, tools, software, and services (GST-inclusive).
Calculate Total GST Input Tax Credits (Item 1B)
Divide GST-inclusive business purchases by 11 to establish total claimable GST credits.
Determine Net Quarterly GST Balance (1A minus 1B)
Subtract 1B credits from 1A GST collected to determine net GST payable to the ATO or refund due.
5. BAS GST Mistakes & Checklist
Claiming GST Input Tax Credits on GST-Free Expenses
Claiming 10% GST credits on bank charges, ASIC fees, or fresh food that never incurred GST in the first place.
Treating GST Collected as Extra Business Revenue
Spending customer GST collected as cash flow profit instead of transferring 1/11th to a dedicated tax saver account.
Failing to Hold Valid Tax Invoices for Supplier Purchases
Claiming GST credits on receipts missing the supplier’s ABN or tax invoice formatting, triggering ATO audit clawbacks.
Mixing Cash and Accruals Accounting Methods
Reporting sales on an invoice date basis while reporting expenses when paid, creating distorted BAS filings.
Quarterly BAS Compliance Checklist
Valid Tax Invoice Archiving ($82.50+ Threshold)
Retain tax invoices showing supplier ABN and GST breakdown for all purchases over $82.50.
Bank Account Reconciliation with Cloud Accounting
Reconcile 100% of bank transactions in Xero/MYOB/QuickBooks before locking quarterly BAS totals.
GST-Free & Input Taxed Expense Audit
Ensure bank fees, residential rent, international software, and fresh food are excluded from 1B credits.
Quarterly ATO BAS Lodgment Calendar Sync
Set lodgment reminders for 28 Oct (Q1), 28 Feb (Q2), 28 Apr (Q3), and 28 Jul (Q4).
6. Annual Quarterly BAS Calendar Timeline
Quarter 1 BAS Lodgment Due
Lodge Q1 BAS covering July – September sales and purchases.
Quarter 2 BAS Lodgment Due
Lodge Q2 BAS covering October – December sales and purchases.
Quarter 3 BAS Lodgment Due
Lodge Q3 BAS covering January – March sales and purchases.
Quarter 4 BAS Lodgment Due
Lodge Q4 BAS covering April – June sales; finalize annual GST reconciliation.
Disclaimer: This BAS GST calculator and guide are provided for general educational and informational planning purposes only. GST rates (10%), 1/11th credit rules, tax invoice requirements ($82.50), and lodgment due dates reflect 2026–27 Australian Taxation Office guidelines. This page does not constitute formal accounting or BAS agent advice.
Charlotte Smith
Senior Personal Finance & Taxation Specialist at AussieSpot
Charlotte Smith is the lead personal finance advisor and workplace specialist at AussieSpot. Charlotte has over 12 years of experience helping Australian households build budgets, plan savings goals, and manage living costs.
Frequently Asked Questions (FAQ)
What is a Business Activity Statement (BAS) and who must lodge it?
A Business Activity Statement (BAS) is a quarterly or monthly reporting form submitted to the ATO by businesses registered for Goods and Services Tax (GST). It reports GST collected, GST input tax credits, PAYG withholding tax from employee wages, and PAYG quarterly tax instalments.
How is 10% GST calculated using the 1/11th rule?
GST included in a total GST-inclusive sales price is exactly 1/11th of the total price (e.g. $110 total price ÷ 11 = $10 GST). To find the GST-exclusive price, divide the total GST-inclusive price by 1.10.
What is the difference between Cash Basis and Accruals Basis GST reporting?
Under Cash Basis, you report GST in the quarter you physically receive payment from clients or pay suppliers. Under Accruals Basis, you report GST in the quarter you issue invoices or receive supplier bills, regardless of when cash changes hands.
What happens if input tax credits exceed GST collected on sales?
If GST paid on business purchases (1B) exceeds GST collected from sales (1A), the ATO refunds the difference directly to your business bank account, typically within 14 business days of digital lodgment.
What valid tax invoice requirements apply for claiming GST credits above $82.50?
To claim GST input tax credits for purchases over $82.50 (inclusive), you must hold a valid tax invoice containing the supplier’s name, ABN, invoice date, description of items, total price, and GST amount.