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.

→ Related: Best Business Bank Accounts for Australian Tradies 2026 — compare fees, features and zero-fee options.

→ Related: Best Business Bank Accounts for Australian Tradies 2026 — compare fees, features and zero-fee options.

What Goes on a Tradie BAS — The Key Fields

BAS Lodgement Dates — Never Miss These

What Happens If You Miss a BAS Deadline?

The ATO charges a Failure to Lodge penalty — currently $313 per 28-day period the BAS is overdue, up to a maximum of $1,565. They also charge General Interest Charge (GIC) on any unpaid amount at approximately 11% per annum. If you cannot pay on time, lodge the BAS anyway (to avoid the FTL penalty) and contact the ATO to arrange a payment plan.

## BAS Lodgement Timeline: When Tradies Actually Need to Lodge The ATO doesn't give you a choice about timing—if you're GST-registered, your BAS is due by the 21st of the month following the end of your quarterly period. Here's how it breaks down for the 2025-26 financial year: **Quarter 1 (1 July – 30 September):** Due 21 October **Quarter 2 (1 October – 31 December):** Due 21 January **Quarter 3 (1 January – 31 March):** Due 21 April **Quarter 4 (1 April – 30 June):** Due 21 July Missing this deadline costs you. The ATS applies penalties starting at 10% of the unpaid amount if you're late, plus interest charges that compound daily. For a tradie earning $150,000 annually and collecting $15,000 in GST per quarter, being even one month late could cost you $1,500 in penalties alone. The smart move is to lodge early. Many tradies lodge within the first week of their quarter ending, which gives them breathing room and keeps cash flow predictable. If you're using accounting software like Xero or Tradify, you can automate a lot of this tracking, which means your numbers are ready to go the moment the quarter ends. ## Common BAS Mistakes Tradies Make (And How to Avoid Them) Getting your BAS wrong is easier than you'd think, and the ATO catches these errors regularly. Here are the mistakes we see tradies making repeatedly: **Mixing up GST collected vs. GST paid** Your BAS box 1A (GST collected) should only include GST you've actually invoiced to clients. If you haven't charged GST on a job, it doesn't go here—full stop. Similarly, box 1B (GST paid on purchases) only includes GST you've paid on business expenses. A common error is claiming GST on personal purchases or including GST on items that aren't actually deductible. **Forgetting to account for cash jobs** If you're a sparky, plumber, or chippy doing cash work, you still need to include GST if you're registered. Just because it's cash doesn't mean it's GST-free. Many tradies skip this and end up underpaying their BAS, which triggers an ATO audit. **Not tracking fuel and vehicle expenses properly** The ATO's current mileage rate for 2025-26 is **88 cents per kilometre**. You can claim this as a flat rate, or you can track actual fuel, maintenance, and repairs. Don't do both—pick one method and stick with it. If you're claiming actual expenses, keep every receipt. If you're using the km rate, keep a logbook showing business trips. We've seen tradies claim vehicle expenses they can't back up, and it's a quick way to get audited. **Missing input tax credits on mixed-use items** If you buy a tool that's used 80% for business and 20% for personal use, you can only claim GST on the 80%. The same applies to phone bills, internet, and vehicle expenses. Be honest about the split—the ATO has data and they cross-reference. **Lodging late without notifying the ATO** If you can't meet the deadline, lodge what you can and contact the ATO. They're more lenient if you're proactive than if they have to chase you. ## BAS Reporting Categories: What Goes Where Understanding which income and expenses go into which BAS box prevents costly mistakes. Here's the breakdown for Australian tradies: | **BAS Box** | **What It Includes** | **Tradie Example** | |---|---|---| | **1A** | GST collected from customers | Invoice to client for $11,000 inc GST = $1,000 goes here | | **1B** | GST paid on business purchases | Buy tools for $550 inc GST = $50 goes here | | **7** | Total income from all sources (GST-inclusive) | All invoices + cash jobs + subcontractor payments | | **8** | Business purchases and expenses | Materials, fuel, rent, insurance, phone bills | | **10** | Capital purchases (assets over $20,000) | Used to calculate depreciation; report separately on tax return | | **11W** | Wages and PAYG withholding | If you employ staff, report gross wages and tax withheld | The key rule: **every dollar in = every dollar accounted for**. The ATO cross-references your BAS boxes with your tax return, so inconsistencies get flagged immediately. ### Frequently Asked Questions Getting your BAS right isn't complicated once you've done it a couple of times. The main thing is consistency: invoice the same way every time, categorise expenses the same way, and lodge on time. Doing this keeps you off the ATO's radar and makes tax time significantly simpler.