Introduction
GST. Three letters that make most tradies' eyes glaze over. But getting GST wrong doesn't just annoy your accountant—it can cost you thousands of dollars a year in lost profit, ATO penalties, or both.
Here's the thing: GST for tradies isn't actually complicated. The rules are straightforward once you understand them. The problem is that most tradies learned their trade from an apprenticeship, not a business degree, and nobody sat them down and explained how tax works when you're running your own show.
In this guide, we'll cover everything an Australian tradie needs to know about GST in 2026—when you need to register, how to calculate it correctly on your quotes and invoices, common mistakes that trigger ATO audits, and how tools like a tradie quoting app can handle the maths automatically so you never get it wrong.
GST Basics: What Every Tradie Needs to Know
What Is GST?
Goods and Services Tax (GST) is a 10% tax added to the price of most goods and services sold in Australia. As a registered business, you collect GST from your clients and pass it on to the ATO. You also get to claim back the GST on business purchases (like materials from Bunnings).
Do You Need to Register for GST?
You must register for GST if:
- Your business turnover (total income, not profit) is $75,000 or more per year
- You expect it to reach $75,000 in the current financial year
You can voluntarily register even if you're under $75,000. Some tradies do this to claim GST credits on materials and tools.
Pro Tip: If you're a sole trader earning $70,000 and growing, register now. Hitting the threshold and not being registered means you owe the ATO back-GST, and that's a nasty surprise.
The $75,000 Threshold Trap
A common mistake: tradies confuse turnover with profit. If you charge $80,000 in a year but your expenses are $40,000, your turnover is still $80,000—not $40,000. You're over the threshold and must be GST-registered.
How GST Works on Your Quotes and Invoices
This is where most tradies get confused—and where mistakes cost real money.
The Two Ways to Quote
GST-Inclusive Pricing: You quote a total price that already includes GST. The client sees one number.
- Example: "Deck Build — $11,000 (inc. GST)"
- The actual price is $10,000 + $1,000 GST = $11,000
GST-Exclusive Pricing with GST Added: You show the base price, then add GST as a separate line.
- Example: "Deck Build — $10,000 + GST ($1,000) = $11,000"
Both are valid, but showing the GST breakdown is strongly recommended. It looks more professional, leaves no ambiguity, and makes your BAS reporting easier.
The Costly Mistake: Forgetting to Add GST
This is the number one GST error tradies make. You quote "$5,000" for a job without thinking about GST. The client pays $5,000. But you're GST-registered, which means 1/11th of that total ($454.55) belongs to the ATO.
Your actual revenue? $4,545.45. You just gave the taxman a slice of what you thought was your profit.
How QuoteMate Handles It
When you create a quote or invoice in QuoteMate, GST is calculated automatically on every line item. The document clearly displays:
- Subtotal (ex-GST)
- GST (10%)
- Total (inc-GST)
There's no mental maths, no forgetting, and no ambiguity. The client sees exactly what they're paying, and you know exactly what's yours and what's the ATO's.
GST on Materials: Claiming It Back
One of the biggest advantages of being GST-registered is claiming GST credits on your business purchases.
How It Works
When you buy materials from Bunnings (or any supplier), you pay GST on those purchases. As a registered business, you can claim that GST back on your BAS.
Example:
- You buy $5,500 (inc. GST) worth of timber from Bunnings.
- The GST component is $500.
- You claim that $500 back as a GST credit on your next BAS.
What You Can Claim GST On
- Materials (timber, concrete, fasteners, paint, etc.)
- Tools and equipment
- Vehicle expenses (fuel, servicing, rego — business portion)
- Phone and internet (business portion)
- Software subscriptions (including your quoting app)
- Insurance
- Workwear and PPE
What You Can't Claim GST On
- Wages (if you employ people)
- Bank fees (GST-free)
- Government charges and licences (some are GST-free)
- Private expenses
Pro Tip: Keep every receipt. Digital copies in an app are fine—the ATO accepts electronic records. QuoteMate tracks your material costs with real-time Bunnings prices, giving you an accurate record of what you've spent.
Understanding Your BAS (Business Activity Statement)
If you're GST-registered, you lodge a BAS either quarterly or monthly. This is where you report:
- GST Collected — the total GST you charged on your quotes and invoices
- GST Paid — the total GST you paid on business purchases
- The Difference — if you collected more than you paid, you owe the ATO. If you paid more than you collected (common during big material purchases), the ATO owes you.
A Simple Example
Quarter: January to March 2026
| | Amount | GST Component | |---|--------|--------------| | Total invoiced to clients | $55,000 | $5,000 | | Total business purchases | $22,000 | $2,000 | | Net GST owed to ATO | | $3,000 |
You collected $5,000 in GST from clients and paid $2,000 in GST on materials. You owe the ATO the difference: $3,000.
The "I Forgot to Set Money Aside" Problem
This is the second biggest GST trap. You collect $5,000 in GST over the quarter, but because it sat in your everyday account, you spent it. Now the BAS is due and you owe $3,000 you don't have.
The Fix: Open a separate bank account. Every time you get paid, transfer 10% of the GST-inclusive total into that account. When BAS time comes, the money is there waiting.
Common GST Mistakes That Cost Tradies Money
1. Quoting Ex-GST to Residential Clients
Residential clients (mums and dads) expect the price you quote to be the price they pay. If you quote "$10,000" and then slap "$1,000 GST" on the invoice, they'll be unhappy—even though you're legally correct. Always make it clear upfront whether your price includes GST or not.
2. Not Claiming GST Credits on Materials
If you're GST-registered and buying materials but not claiming the credits, you're leaving money on the table. That 10% adds up fast when you're spending thousands on timber, concrete, and hardware every month.
3. Mixing Personal and Business Expenses
Using one bank account for everything makes it nearly impossible to accurately separate GST claims. The ATO can (and does) audit this. Keep business and personal finances separate.
4. Getting the Maths Wrong
Calculating GST should be simple (divide by 11 to find the GST in a GST-inclusive price, or multiply by 1.1 to add GST), but when you're doing it manually across 30 line items at 9 PM, errors happen. This is exactly why an ABN GST calculator built into your quoting app is worth its weight in gold.
5. Not Including Your ABN on Invoices
If you're GST-registered, your ABN must appear on every tax invoice. Without it, your client can't claim GST credits on their end (relevant for commercial jobs), and it raises red flags with the ATO.
Tax Invoices vs Regular Invoices
If you're GST-registered, your invoices are legally "tax invoices" and must include:
- Your business name and ABN
- The date of issue
- A description of the goods or services
- The GST amount (either shown separately or stated as "Total includes GST")
- The total price
For invoices over $1,000, you also need:
- The buyer's name and address
- The quantity of each item
QuoteMate's invoices include all of these fields by default. When you fill in your business settings (ABN, business name, address), every document you generate is a compliant tax invoice.
Frequently Asked Questions
Q: What if I'm not registered for GST—do I still need to worry about this?
A: If your turnover is under $75,000 and you haven't voluntarily registered, you don't charge or collect GST. However, you also can't claim GST credits on your purchases. Keep an eye on your turnover—if you're approaching $75,000, register before you hit it.
Q: Should I quote GST-inclusive or GST-exclusive?
A: For residential clients, GST-inclusive is generally better—it avoids sticker shock. For commercial clients (builders, other businesses), GST-exclusive with GST shown separately is standard. QuoteMate shows the full breakdown either way.
Q: How often do I need to lodge a BAS?
A: Most small businesses lodge quarterly. If your turnover is over $20 million, you lodge monthly. Your accountant or the ATO portal will confirm your lodgement schedule.
Q: Can I use QuoteMate records for my BAS?
A: QuoteMate's invoices and quotes include itemised GST breakdowns, making it easy to report your GST collected. For a complete BAS, you'll also need records of your business purchases (material receipts, fuel, subscriptions, etc.).
Key Takeaways
- Register for GST if your turnover exceeds $75,000 — turnover means total income, not profit.
- Always show GST on your quotes and invoices — it prevents confusion and protects your margin.
- Claim GST credits on all business purchases — materials, tools, fuel, insurance, and software.
- Set aside GST in a separate account — so you're never caught short at BAS time.
- Use software that calculates GST automatically — manual maths at 9 PM leads to expensive errors.
Conclusion
GST doesn't have to be a headache. The rules are simple: charge 10%, claim back what you spend on business purchases, and pay the difference to the ATO each quarter. The key is having a system that handles the calculations for you so you're not second-guessing the maths on every quote and invoice.
QuoteMate calculates GST automatically on every line item, displays it clearly on professional PDFs, and keeps your records clean for BAS time. Combined with a separate GST bank account and a good accountant, you'll never have a GST surprise again.
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