A good battery invoice lets a stranger reconstruct the deal in thirty seconds. The customer should see what the battery system costs, what the federal discount takes off, and what they pay.
A layout that works
| Line | Example content |
|---|---|
| Battery system supplied and installed | Full price, GST shown |
| Less STC discount (assignment of STCs) | Number of STCs and dollar value |
| Balance payable by customer | Total after discount |
Name the battery model, usable capacity in kWh, the installation address and the installation date. Those match the assignment form and the claim, which is what an auditor checks first.
Details that avoid trouble
Match the STC count. The count on the invoice should equal what the calculator produces for that battery and date. Use the battery STC calculator and keep the output with the job file. The factor is 6.8 at the time of writing for 2026 installs, with the tiered 100 percent, 60 percent and 15 percent structure across 14, 28 and 50 kWh.
Say it is an assignment. The customer is transferring their STCs, not receiving a government cheque. Wording such as “STCs assigned to installer” keeps that straight and lines up with the battery assignment form.
Do not promise a fixed cashback. If the STC price moves, your discount value is your call, but the customer’s deal should be fixed on the invoice.
Keep GST consistent. How the discount interacts with GST is covered in battery rebate GST treatment.
Common invoice mistakes
The most frequent errors are quoting the net price only, so the STC value is invisible; showing a discount that was calculated at a different factor from the one that applies on the installation date; and leaving the usable capacity off, so the invoice cannot be tied to the claim. Another is a discount rounded up for the customer’s benefit while the claim is for fewer STCs. Because STCs are rounded down, a 13.5 kWh battery at 6.8 creates 91 STCs, not 92, and the invoice should say 91.
If the sale is to a business, add the ABN and show GST on the full price. If the customer is financing the balance, the finance provider will usually want the same itemised layout.
What this means for installers
The invoice, assignment form, photos and claim are four documents telling one story. If they disagree on capacity, serial, date or STC count, you invite a query. The STC assignment form guide and RCTI, GST and ABN guide cover the neighbouring paperwork.
From the desk: if the customer upgrades the battery between quote and install, reissue the invoice and the assignment form. A form signed for 10 kWh will not support a claim for 13.5 kWh.
Read the full scheme on battery STCs, and check today’s buy rate on pricing before setting your discount.