Australia's solar installation industry is one of the highest-volume sectors for the federal government's Small-scale Renewable Energy Scheme (SRES). The scheme creates a financial mechanism — Small-scale Technology Certificates (STCs) — that effectively subsidises the upfront cost of rooftop solar systems. For bookkeepers servicing solar installers, STCs are the defining complexity: they are not simply a discount, and their revenue and GST treatment must be handled correctly from the invoice onwards.
What Are STCs and How Are They Created?
When a solar PV system is installed and commissioned, the installer (or the homeowner, if they choose to manage it) can create STCs through the Clean Energy Regulator's (CER) Renewable Energy Certificate Registry. The number of STCs created depends on the system's capacity and the zone-based deeming period (calculated to 2030).
In practice, most residential customers assign their right to create STCs to the installer at the point of sale in exchange for a discount on the system price. The installer then sells those STCs — either on the open STC spot market or through a registered agent — to recoup the discount given to the customer.
Revenue Recognition: Upfront Assignment vs. Cash Receipt
There is a timing mismatch between when the STC discount is given to the customer and when the installer receives cash from the STC sale. The bookkeeping approach must reflect the economic substance:
At installation (invoice date):
- Record the full system price as revenue (e.g., $12,000).
- Record the STC discount as a reduction of the invoice price (e.g., -$3,000 STC assignment value).
- Net customer invoice: $9,000.
When STCs are sold to the market:
- Debit bank / receivable for the STC proceeds (e.g., $3,000).
- Credit the STC asset account or STC receivable opened at invoice date.
If the STC market price at sale differs from the estimate used at invoice date, post the variance to an STC gain/loss income account. STC spot prices fluctuate — installers who hold STCs rather than selling immediately bear price risk.
An alternative approach used by some installers is to recognise STC income only when the certificates are sold and cash is received, treating the upfront discount as a cost reduction. Both approaches can be defensible — the critical requirement is consistency across periods and adequate disclosure in the chart of accounts.
GST Treatment of STCs
STCs are financial instruments — specifically, they are "registered emissions units" as defined in the Clean Energy Act 2011. The supply of STCs is a GST-free financial supply under item 9 of the GST-free financial supplies table in the GST Regulations. This means:
- The installer does not charge GST when selling STCs to a registered agent or on the open market.
- The STC proceeds are not included in the GST turnover figure for BAS purposes.
- However, the installer cannot claim ITCs on costs that relate solely to the supply of STCs (as these are financial supplies that are GST-free with no ITC entitlement under Div 40A of the GST Act).
In practice, the costs of creating and selling STCs (mostly administrative — CER registration fees, agent fees) are minor. But the bookkeeper must ensure the STC proceeds are not being included in taxable sales on the BAS, and that agent fees paid for STC lodgement are not being claimed as full ITCs without apportionment.
The installation labour and panels themselves are taxable supplies — GST applies to the customer invoice (net of the STC discount) at the standard rate.
Commercial vs. Residential Installations
Commercial solar installations differ from residential in several important ways:
- The customer is usually a GST-registered business and can claim the GST on the system as an ITC. The installer issues a tax invoice including GST.
- Large commercial systems (>100 kW) create Large-scale Generation Certificates (LGCs) rather than STCs — LGCs operate under a different scheme with different bookkeeping treatment.
- Progress billing is common on large commercial projects: the installer bills at milestones (design sign-off, equipment delivery, installation completion, grid connection). Revenue is recognised at each milestone, and WIP tracking is required if any milestone spans a reporting period.
Subcontractor Labour and PAYG Obligations
Residential solar installation is labour-intensive, and most medium-to-large installers rely heavily on subcontractor electricians and roofers. The bookkeeper must assess whether each subcontractor arrangement creates a PAYG withholding obligation.
From 1 July 2021, the Taxable Payments Reporting System (TPRS) covers the building and construction industry, which includes solar installation. Businesses that engage contractors in this sector must lodge a Taxable Payments Annual Report (TPAR) by 28 August each year, reporting total payments to each contractor. Failure to lodge attracts penalties.
Where a subcontractor does not quote an ABN, the installer must withhold 47% from the payment (no-ABN withholding) and remit to the ATO. This is a common compliance gap for solar installers who engage labour hire at short notice for large commercial installs.
Vehicle and Equipment Fleet Depreciation
Solar installation businesses typically operate a fleet of panel-laden vans and specialised equipment (panel lifters, inverter test equipment, safety rigs). Key depreciation considerations:
- Vans and utes used exclusively for business — claim the full depreciation deduction under Div 40 of the ITAA 1997.
- Mixed-use vehicles — apportion based on a logbook maintained for at least 12 continuous weeks.
- Specialised installation equipment — check ATO Tax Ruling TR 2023/1 for effective lives. Panel lifting equipment effective life is typically 10 years; inverter testing equipment 5–8 years.
Small business entities may apply simplified depreciation rules under Subdiv 328-D, pooling assets and applying 15% in year one and 30% diminishing value thereafter.
Legislation and Further Reading
- Renewable Energy (Electricity) Act 2000 — STC scheme framework
- Clean Energy Act 2011 — registered emissions units definition
- A New Tax System (Goods and Services Tax) Act 1999 — GST-free financial supplies
- Income Tax Assessment Act 1997, Div 40, Subdiv 328-D
- ATO — Taxable Payments Annual Report (TPAR) for building and construction
- Clean Energy Regulator — STC registry and spot market information