Kalaro Guides · GST & Compliance
Business Activity Statements (BAS)
The BAS is where GST, PAYG withholding and instalments all come together into one regular lodgment. This is what it actually covers and how to stay ahead of it.
What a BAS actually reports
A Business Activity Statement isn't a single tax. It's a reporting form that bundles several obligations into one lodgment, so the ATO gets a regular snapshot of what a business owes and is owed. Depending on your registrations, a BAS can include:
- GST: the goods and services tax collected on sales, less GST credits claimed on business purchases
- PAYG withholding: tax withheld from employees' wages and remitted to the ATO
- PAYG instalments: prepayments toward your own income tax liability, based on business or investment income
- FBT instalments: quarterly prepayments toward an anticipated fringe benefits tax liability, where applicable
- Luxury car tax and wine equalisation tax: for businesses that deal in these specifically
Most small businesses will only see GST and PAYG withholding on their BAS, but the form scales up as a business grows.
Who needs to lodge
You need to register for GST, and therefore start lodging BAS, once your business's GST turnover reaches $75,000 (or $150,000 for non-profit organisations), or immediately if you provide taxi, rideshare or limousine travel, regardless of turnover. Registration is optional below that threshold, but once you're registered, lodging becomes compulsory even in a quarter with no activity. A "nil" BAS still needs to be lodged.
How often you lodge
Lodgment frequency is generally set by your GST turnover:
- Quarterly: the default for most small businesses, GST turnover under $20 million
- Monthly: compulsory once GST turnover reaches $20 million, or optional if you'd prefer more frequent, smaller lodgments
- Annually: available in limited circumstances, generally for voluntarily registered businesses under the threshold
| Quarter 1 (Jul to Sep) | 28 October |
| Quarter 2 (Oct to Dec) | 28 February |
| Quarter 3 (Jan to Mar) | 28 April |
| Quarter 4 (Apr to Jun) | 28 July |
Quarter 2 gets a built-in extension to 28 February rather than the usual 28-day window, to account for the holiday period. Monthly BAS is due on the 21st of the following month. Lodging through a registered tax or BAS agent generally adds a further concessional period on top of these dates.
Working out what you owe
For most transactions, GST is calculated as one-eleventh of the GST-inclusive sale price. That's because a 10% tax added to a base price means GST makes up 1/11th of the final figure, not 1/10th. Your net GST position for the period is:
GST collected on sales minus GST credits on purchases = Net GST payable (or refundable)
Whether you report on a cash or accruals basis changes when a transaction counts. Cash basis picks it up when money actually moves, accruals basis when the invoice is issued or received. Turnover under $10 million generally gives you the choice; above that, accruals reporting is compulsory.
Where businesses go wrong
- Claiming GST credits on purchases that don't carry GST at all: bank fees, residential rent, and many government charges are GST-free or input-taxed
- Mixing up the cash and accruals reporting method partway through the year without adjusting for the transition
- Forgetting that a BAS is still due even when trading has been quiet. A nil lodgment avoids failure-to-lodge penalties
- Treating PAYG instalments as optional. They're a prepayment of tax you'll owe anyway, and skipping them just shifts the pain to your income tax bill
Frequently asked questions
What happens if I lodge a BAS late?
The ATO can apply a failure-to-lodge penalty, calculated in penalty units for each 28-day period the statement is overdue, plus general interest charge on any amount unpaid. Lodging through a registered agent, even late, is usually better than not lodging at all.
Do I need to lodge a BAS if I'm not registered for GST?
No. If you're not GST-registered, you don't lodge a BAS. You may still need to report PAYG withholding separately if you employ staff, but that's a different obligation from BAS.
Can I change how often I lodge?
Yes, within limits set by your turnover. Moving from quarterly to monthly voluntarily is generally straightforward, while moving to less frequent lodgment usually requires meeting turnover thresholds and applying to the ATO.
This guide reflects Australian GST and BAS settings current as at 2026 and is general information only. It doesn't take into account your specific circumstances and shouldn't be relied on as tax advice. Confirm current thresholds and due dates before lodging, as these are set by the ATO and can change.