GST calculator for plumbers (Australia)
A plumbing invoice is often a call-out fee, time on site and a list of parts: tapware, valves, fittings, pipe, and sometimes a whole hot water system. If you're GST-registered, every line is a taxable sale at the price you charge, so GST applies to the parts and to the hot water unit as well as your labour.
Worked example: a typical plumber invoice
| Item | Qty | Unit price (ex GST) | Line total |
|---|---|---|---|
| Call-out fee | 1 | $99.00 | $99.00 |
| Labour (hours) | 2 | $120.00 | $240.00 |
| Mixer tap, supplied | 1 | $189.00 | $189.00 |
| Isolation valves | 2 | $24.00 | $48.00 |
| Fittings and sundries | 1 | $35.50 | $35.50 |
| Subtotal (GST-exclusive) | $611.50 | ||
| GST (10% of the subtotal) | $61.15 | ||
| Total including GST | $672.65 | ||
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: $672.65 ÷ 11 = $61.15.
GST credits plumbers 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:
- parts and fittings from the plumbing supplier, with tax invoices over $82.50
- drain cameras, jetters and other equipment (a capital purchase if it costs more than $1,000)
- the business-use share of your van running costs
- waste disposal and tip fees that include GST
- uniforms with your business logo
Common GST mistakes
- Treating a hot water system you supply as a pass-through cost with no GST. If you're registered, it's part of your taxable sale.
- Forgetting to claim the GST on parts because the receipts were lost. Ask your supplier for a copy of the tax invoice; most can reprint them.
- Not dating invoices. The issue date is one of the things a tax invoice must show.
Questions
Is an after-hours surcharge taxable?
Yes. It's part of the price of your service, so if you're registered, GST applies to it like the rest of the job.
Can I claim GST on a new van?
If you're registered and use it for the business, you can claim a GST credit for the business-use share, with a tax invoice. Cars have a GST credit limit; check the ATO's car limit for the year.
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 plumbers · 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