GST calculator for carpenters (Australia)
Carpentry jobs are often bigger and longer than a single call-out, so they're commonly invoiced as a deposit, progress claims and a final invoice. Each invoice is a separate tax invoice if you're registered: GST is worked out on the amount of that invoice, and the timber, fixings and hardware you supply are part of the taxable price.
Worked example: a typical carpenter invoice
| Item | Qty | Unit price (ex GST) | Line total |
|---|---|---|---|
| Labour: deck frame and boards (hours) | 16 | $95.00 | $1,520.00 |
| Treated pine framing | 1 | $640.00 | $640.00 |
| Hardwood decking boards | 1 | $1,820.00 | $1,820.00 |
| Stainless screws and fixings | 1 | $185.00 | $185.00 |
| Skip bin hire (recharged) | 1 | $420.00 | $420.00 |
| Subtotal (GST-exclusive) | $4,585.00 | ||
| GST (10% of the subtotal) | $458.50 | ||
| Total including GST | $5,043.50 | ||
Figures are an illustration, not suggested prices. GST is worked out on the subtotal and rounded to the cent (the ATO's "total invoice" rounding approach). Check: $5,043.50 ÷ 11 = $458.50.
GST credits chippies commonly claim
If you're registered for GST, you can generally claim a GST credit for the GST in business purchases (the business-use share for mixed-use items), as long as you hold a tax invoice for purchases over $82.50 including GST. Common examples:
- timber, sheet goods and hardware from the yard, with tax invoices
- power tools and nail guns (record big items as capital purchases)
- skip bin and tip fees you pay
- the business-use share of your ute, trailer and fuel
- safety gear and PPE
Common GST mistakes
- Leaving GST off a recharged cost like skip bin hire. If you're registered and you bill it to the customer, it's part of your taxable sale.
- Taking a deposit and forgetting it in the next BAS. If you account for GST on a non-cash (accrual) basis, an invoice or payment for a deposit can trigger GST when it's issued or received. Ask your tax agent which applies to you.
- Progress claims that don't say what stage they cover, which makes disputes harder.
Questions
Do I charge GST on each progress claim?
If you're registered, yes: each progress claim is a taxable sale for that amount. Show the GST on each one.
The customer supplies the timber. What do I charge GST on?
Only on what you sell them: your labour and anything you supply. Materials the customer buys directly aren't part of your sale.
The rules in one place
- GST is 10%. The GST in a GST-inclusive price is the price ÷ 11.
- You must register at A$75,000 GST turnover (current month plus the previous 11, or projected for the next 12), within 21 days. Taxi and rideshare drivers must register regardless of turnover.
- If a customer asks for a tax invoice, you must give one within 28 days, unless the sale is A$82.50 (incl. GST) or less.
- Quarterly BAS for FY2026-27 is due 28 Oct 2026, Tue 2 Mar 2027, 28 Apr 2027 and 28 Jul 2027 (calculator).
Sources (checked 17 Oct 2026): ATO Tax invoices (updated 18 Sep 2026); ATO Registering for GST; ATO When you can claim a GST credit.
General information, not tax advice. It doesn't take your circumstances into account. Check with the ATO or a registered tax or BAS agent.
Related
- Free printable invoice template for carpenters · Full GST calculator · BAS due dates · PAYG instalments
From Quillroo
- Tradie GST & BAS Workbook FY2026-27: paid spreadsheet: sales, purchases and BAS labels for a quarter, with trade expense categories
- AU Invoice Chaser for n8n: sends polite payment reminders from a Google Sheet
- 5 payment reminder email templates: free PDF