Three questions sit under this one: can you see an STC number on the invoice, how do you read the STC line on a quote, and how does the discount appear on the paperwork. They share a short answer, so here they are together.
What a clear STC line shows
A well-prepared quote or invoice gives you three numbers:
- The number of STCs your system is expected to create.
- The dollar value the installer is using for each STC.
- The total deducted from the price.
Typical wording is “Less STC discount (45 STCs at $38)” or a single line headed “Small-scale technology certificates”. If you only see “government rebate” with a single figure, ask for the count and the unit value. Our guide to how the STC discount is presented on a quote shows what good looks like.
Where is the STC number?
People searching for “the STC number on my invoice” usually mean one of two things. The count is on your quote. The serial numbers are not. Each certificate has a serial number in the REC Registry run by the Clean Energy Regulator, recorded when the installer creates it, and you will not normally see those unless you ask for the creation details. If you want proof they were created, see how to check if your installer claimed your STCs.
Checking the count yourself
The count is a calculation: system size in kW, multiplied by the zone rating for your postcode, multiplied by the deeming years left, rounded down.
| Item | Example |
|---|---|
| System size | 6.6 kW |
| Zone rating (zone 3, such as Sydney or Brisbane) | 1.382 |
| Deeming years (2026 install) | 5 |
| STCs | 6.6 x 1.382 x 5 = 45.6, rounded to 45 |
At the roughly $38 to $40 market range at the time of writing, 45 STCs is about $1,700 to $1,800 of value. The STC calculator will do the arithmetic for your postcode, and our zone and deeming guide explains the inputs. If the quote count is noticeably lower than the calculator, ask why.
What this means for you
Keep the quote and the final invoice together. They should agree on the STC count, and the final invoice should reflect the real system size installed. For how GST sits alongside the discount, read STC discount and GST on the invoice. See the homeowners guide for the full picture, and installers can see what a claim is worth on our pricing page or the STC trading overview.