How to Lodge Your BAS with GST โ Step by Step Guide 2026
Lodging your Business Activity Statement (BAS) correctly is one of the most important GST compliance tasks for Australian businesses. This plain-English guide walks you through every step โ from calculating your GST to submitting online through the ATO.
What is a Business Activity Statement (BAS)?
A BAS is a form that GST-registered businesses submit to the ATO to report and pay several tax obligations at once, including GST collected on sales, GST credits on purchases, Pay As You Go (PAYG) withholding from employees, and PAYG instalments on business income.
When Must You Lodge Your BAS?
Most businesses lodge quarterly. The standard quarterly due dates are:
| Quarter | Period | Due Date |
|---|---|---|
| Q1 | 1 July โ 30 September | 28 October |
| Q2 | 1 October โ 31 December | 28 February |
| Q3 | 1 January โ 31 March | 28 April |
| Q4 | 1 April โ 30 June | 28 July |
Step 1: Calculate GST Collected on Sales
Total all GST-taxable sales for the period and calculate the 10% GST you collected:
Total Taxable Sales ร 10% = GST Collected
Add up all GST-taxable sales
Include all sales where you charged GST. Exclude GST-free sales (fresh food, medical services, exports) and input-taxed sales (rent).
Calculate GST collected
Multiply total taxable sales by 0.10. This is the amount you must remit to the ATO for Box 1A.
Record total sales including GST-free
Box G1 on your BAS asks for total sales โ include both taxable AND GST-free supplies here.
Step 2: Calculate Your Input Tax Credits (GST on Purchases)
Input tax credits are the GST you paid on business purchases โ you can claim these back to reduce your GST liability:
Total Business Purchases รท 11 = GST Credits Claimable
You can only claim GST credits on purchases that are:
- For use in your business (not private or personal use)
- From a supplier registered for GST
- Supported by a valid tax invoice (for purchases over $82.50)
Step 3: Calculate Net GST and Lodge
Net GST = GST Collected (1A) โ GST Credits (1B)
Log in to ATO Online Services
Access via myGov โ ATO Online Services. Your BAS will be pre-populated with some figures.
Enter your figures
Fill in G1 (total sales), 1A (GST collected), 1B (GST credits). The ATO system calculates the net.
Review and submit
Check all figures, declare they're correct, and submit. Payment is due by the same date as lodgement.
Pay or receive refund
If you owe GST, pay via BPAY, credit card or direct debit. If you're owed a refund, the ATO pays within 14 days.
Penalties for Late BAS Lodgement
Pro Tips for BAS Lodgement
- Use accounting software like Xero, MYOB or QuickBooks to auto-calculate your BAS figures
- Reconcile your bank account before lodging to ensure accuracy
- Keep all tax invoices for at least 5 years โ the ATO can audit you during this period
- Set a calendar reminder 2 weeks before each BAS due date
- Consider engaging a registered BAS agent for the extended deadline benefit
The core BAS formula is simple: GST Collected (1A) minus GST Credits (1B) = Net GST payable. Get your bookkeeping current, lodge on time and pay by the due date to avoid penalties and interest.