How to Invoice as a Sole Trader Plumber (Complete Guide)
Key Requirement: If you're registered for GST (mandatory once you earn $75,000+), your invoices MUST include your ABN, GST amount, and be called a "Tax Invoice." Missing these makes the invoice legally invalid.
What Must Be on a Plumbing Invoice (Australia)
The ATO requires specific information on invoices. Missing any of these can mean you don't get paid, or worse, cop a fine during an audit:
For invoices under $1,000:
- Your business name and ABN
- Date of issue
- Description of work performed
- Total amount (including GST if registered)
- The words "Tax Invoice" (if GST registered)
For invoices over $1,000 (additional requirements):
- Customer's name and address
- Invoice number (sequential)
- GST amount shown separately
- Each line item's price and quantity
Invoice Timing — When to Send
The golden rule: invoice immediately after completing the job. Not at the end of the week. Not at the end of the month. The moment you finish, while you're still in the van outside their house.
Why? Because:
- The customer remembers the work and is happy with the result right now
- You remember the exact work done and materials used right now
- Payment terms start from invoice date — delay the invoice, delay the payment
- You won't forget to invoice (it happens more than you think)
Payment Terms for Plumbers
| Customer Type | Recommended Terms | Why |
|---|---|---|
| Residential (homeowner) | Due on completion | They're home, they can pay now |
| Residential (tenant) | 7 days | May need to forward to landlord/agent |
| Property manager | 14 days | They batch-process payments |
| Builder | 14-30 days | Industry standard (watch for slow payers) |
| Commercial/body corporate | 30 days | Accounts payable cycles |
Getting Paid Faster
- Offer tap-and-go on site: A $30 card reader pays for itself in one week of faster payments
- Include bank details on every invoice: BSB, account number, and reference clearly visible
- Send a payment link: If your invoicing software supports it, a "Pay Now" button increases payment speed by 40%
- Follow up at 7 days: A friendly "just checking you received my invoice" text works wonders
Common Invoicing Mistakes
- Forgetting to include ABN (makes the invoice invalid for GST purposes)
- Not numbering invoices sequentially (ATO red flag during audit)
- Vague descriptions ("plumbing work" instead of "Replace mixer tap in kitchen, supply and install Caroma basin mixer")
- Not separating materials from labour (customers want to see the breakdown)
- Invoicing weekly instead of per-job (delays payment and makes disputes harder)
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