What is a BAS and How Do Tradies Lodge It?

If you're registered for GST in Australia, you have to lodge a Business Activity Statement (BAS) — usually every quarter. Most tradies find it confusing at first, but once you understand what it's asking, it takes about 20 minutes. Here's everything you need to know.

What is a BAS?

A Business Activity Statement is a form you send to the ATO that reports how much GST you've collected from clients and how much GST you've paid on your own business purchases. The difference is what you either pay to the ATO or get refunded.

Think of it this way: you charge your clients 10% GST on every invoice. But you also pay GST when you buy tools, fuel, materials and other business expenses. The BAS is where you settle up — you send the ATO the difference between what you collected and what you paid.

Who Needs to Lodge a BAS?

Any business registered for GST must lodge a BAS. You're legally required to register for GST once your annual turnover exceeds $75,000. Most tradies hit this quickly — if you're charging $100+/hour, you'll cross $75k in less than a year of regular work.

When is it Due?

Most small businesses lodge quarterly. Due dates for the 2025–26 year:

If you use a registered BAS agent or tax agent, they typically get an extended deadline. Worth using one if you find it stressful.

What Goes in Your BAS?

G1 — Total sales: The total of all your invoices for the quarter including GST.

1A — GST on sales: The GST portion of your sales. If you invoiced $110,000 total, the GST portion is $10,000 (1/11 of the total).

1B — GST on purchases: The GST you paid on business expenses — tools, materials, fuel, software subscriptions, accounting fees. This reduces what you owe.

Net GST: 1A minus 1B. If you collected $10,000 in GST and paid $3,000 on purchases, you send the ATO $7,000. If you paid more GST on purchases than you collected (unusual but happens), you get a refund.

How to Lodge Your BAS

Three ways to lodge:

• Through your accounting software — Xero and MYOB both connect directly to the ATO and can pre-fill your BAS from your transactions. Fastest option if your books are up to date.
• Through myGov / ATO Online — Log in to the ATO's Business Portal and complete it manually. Works fine if you have a simple situation.
• Through a BAS agent or accountant — They handle everything. Recommended for your first few BAS lodgements or if your situation is complex.

Using Xero or Rounded makes BAS time much less painful — your transactions are already categorised and the software tells you what you owe.

What if You Lodge Late?

The ATO charges Failure to Lodge (FTL) penalties for late BAS submissions. The penalty is one penalty unit ($313 in 2025–26) for each 28-day period (or part thereof) that it's overdue, up to a maximum of 5 penalty units ($1,565). Interest charges also apply on any unpaid amount.

If you genuinely can't pay on time, call the ATO before the due date. They often arrange payment plans for tradies with a good compliance history.