What Is a BAS? Business Activity Statement Explained

What is a BAS?

A Business Activity Statement (BAS) is a form submitted to the Australian Taxation Office by GST-registered businesses. It is used to report and pay several tax obligations in one place — most commonly GST collected on sales, GST credits claimed on purchases, and PAYG withholding from employee wages.

Most small businesses lodge their BAS quarterly, though businesses with higher turnover or those who choose to may lodge monthly. The BAS replaced a range of separate tax forms when the GST system was introduced in 2000.

Who needs to lodge a BAS?

You must lodge a BAS if your business is registered for GST. GST registration is compulsory once your annual GST turnover reaches $75,000 (or $150,000 for non-profit organisations). Businesses below the threshold can register voluntarily — and if you do, you must lodge a BAS.

Taxi and rideshare drivers must register for GST regardless of their turnover.

If you are not registered for GST, you do not lodge a BAS — but you may still need to lodge an Instalment Activity Statement (IAS) if you have PAYG withholding obligations from payroll.

What does a BAS include?

The specific fields on your BAS depend on your tax obligations, but most small business BAS forms include some or all of the following:

The net GST position (1A minus 1B) is what you pay to or receive from the ATO for that period. If you collected more GST than you paid, you owe the difference. If you paid more GST than you collected, you receive a refund.

When is a BAS due?

Quarterly BAS lodgement is the most common frequency for small businesses. Due dates depend on whether you self-lodge or use a registered BAS agent.

Using a registered BAS agent — such as a bookkeeper — gives you access to the extended agent deadlines shown above. This is one of the practical benefits of having your BAS prepared professionally rather than self-lodging.

What happens if you don't lodge on time?

The ATO issues a failure-to-lodge (FTL) penalty for BAS submissions that are late. The penalty is calculated at one penalty unit per 28-day period (or part thereof) that the BAS is overdue, up to a maximum of five penalty units.

As of 2026, one penalty unit is $313. A BAS that is 28 days late attracts a $313 penalty. One that is 56 days late attracts $626, and so on up to $1,565 for the most delayed submissions.

In addition to the FTL penalty, the ATO charges general interest charge (GIC) on any unpaid tax amounts from the due date until payment is received.

The ATO can remit penalties in some circumstances — particularly for first-time offenders or where there was a genuine reason for the delay — but this is not guaranteed and requires a formal request.

Cash vs accrual — which method applies to your BAS?

There are two methods for accounting for GST on your BAS:

Cash basis

You report GST when you receive payment from customers (not when you invoice them) and claim GST credits when you pay your suppliers (not when you receive their invoice). Most small businesses under $10 million in annual turnover can use the cash basis — and it is generally simpler to manage.

Accruals basis

You report GST when you issue an invoice, regardless of whether you have been paid. This is more complex but gives a more accurate picture of your GST obligations at any point in time. Businesses over $10 million in turnover must use the accruals basis.

Your bookkeeper should set up your accounting software to match whichever method applies to your business — inconsistent treatment is one of the most common BAS errors.

Common BAS mistakes to avoid

Claiming GST on GST-free purchases. Not everything has GST. Basic food, medical services, financial supplies, and some education and health items are GST-free — you cannot claim a GST credit on these.

Incorrect GST coding in your accounting software. If transactions are coded to the wrong tax rate, your BAS figures will be wrong. This is why monthly reconciliation matters — errors compound if they are left until quarter end.

Forgetting to include all income. All taxable sales must be reported, including cash sales, online sales, and any barter or contra arrangements that have a taxable value.

Missing the lodgement deadline. The ATO does not send reminders. If you miss the deadline, penalties apply automatically.

Not reconciling your BAS to your accounts. Your BAS figures should reconcile back to your accounting software. If they don't, there is an error somewhere that needs to be found before lodgement.

Should you prepare your BAS yourself?

Technically, you can prepare and lodge your BAS yourself through the ATO's Business Portal or your accounting software. In practice, BAS preparation requires your books to be reconciled, all transactions correctly coded, and GST treatment verified across every purchase and sale for the quarter.

For most small business owners, the time cost of doing this correctly — and the risk of errors that attract ATO attention — makes professional BAS preparation worthwhile. A registered BAS agent also gives you access to extended lodgement deadlines.

advancr includes BAS preparation across all subscription plans, with lodgement available as an add-on. Because your books are reconciled every month, your BAS is ready well before the deadline — no scrambling at quarter end.

Frequently asked questions — BAS Australia