Renewable Energy Certificate Retirement and LGC...

The auditor will ask for one thing you probably do not have. Not the invoice from the retailer. Not the GreenPower brochure. The REC Registry surrender confirmation for every megawatt-hour you counted as zero emissions in your market-based Scope 2 line.

This is the number that trips up first-time market-based reporters under AASB S2. You bought the certificates. You paid the premium. You put the reduced figure in the report. But the certificate is still sitting active in the registry, or the surrender happened in the wrong reporting period, or the vintage year does not line up with the electricity consumption year. Any of those, and the assurance provider will disallow the claim.

We spent a fair chunk of the last twelve months building the retirement ledger inside Carbonly, and the problem is not the mechanics of a single surrender. It is proving, three years later, that 47 individual surrenders across four vintages and three registries lined up with the electricity you consumed at seven business units. That is the renewable energy certificate retirement and LGC surrender tracking problem this post is about.

Why market-based Scope 2 requires certificate surrender evidence

The GHG Protocol Scope 2 Guidance splits electricity accounting into two methods that both have to be reported. Location-based uses the grid emission factor for wherever you consumed the electricity. Market-based uses the emission factor associated with the specific instrument you contracted for. In Australia those instruments are Large-scale Generation Certificates, GreenPower, PPA settlements, and occasionally imported I-RECs or European Guarantees of Origin.

The market-based figure is the one that goes down when you buy certificates. The location-based figure does not move. Both get disclosed. AASB S2 paragraph 29(a)(v) requires this dual disclosure explicitly. So does the ISSB S2 standard it is based on.

Here is the catch. The Scope 2 Guidance is very specific about what counts as a market-based instrument. It has to be a contractual instrument, it has to convey the attributes, it has to be surrendered (retired, cancelled; the words are used interchangeably in the registries) against the claimed consumption, and the surrender has to be exclusive. That last word matters. If two reporters both claim the same MWh, the whole system falls apart. The surrender record is what enforces exclusivity.

An auditor performing an ASSA 5010 walk-through will trace a sample of your claimed renewable MWh back to the surrender confirmations in the REC Registry. If you cannot produce them, the market-based figure is not defensible and the disclosure has to be restated. That has already happened to first-time Group 1 reporters this year, and it will keep happening.

The Australian certificate stack: LGCs, STCs, GreenPower, PPA settlements

Four instruments matter for Australian market-based Scope 2, and they behave differently.

Large-scale Generation Certificates are the workhorse. One LGC represents one MWh of eligible large-scale renewable generation: wind farms, utility solar, hydro. They are created, traded, and surrendered through the Clean Energy Regulator's REC Registry. When you surrender an LGC voluntarily against your Scope 2, the registry records the surrender with a unique identifier, a date, a vintage year, and the surrendering party. That is the piece of paper (well, PDF) the auditor wants.

Small-scale Technology Certificates come from rooftop solar, small wind, and solar hot water installations under 100 kW. They are a completely different animal. STCs act as an upfront financial rebate at the point of installation, and they are typically assigned to the installer or aggregator, not the site owner. You do not usually surrender STCs the way you surrender LGCs. Behind-the-meter solar generation from a rooftop system is treated as zero-emissions for Scope 2 whether or not STCs were created, because you never bought electricity for those kWh in the first place. This is a place we see reporters get tangled, trying to double-count rooftop solar as both a self-generated zero and an STC-backed claim.

GreenPower is a government-accredited voluntary program that sits on top of LGCs. When your retailer sells you GreenPower, they are contractually obliged to surrender LGCs of the correct vintage against your consumption. GreenPower has its own quality overlay: certificates must be from post-1997 generators, must not be double-counted against the LRET compliance obligation, and vintages must fall within a defined window. From the reporter's perspective, GreenPower purchases are usually simpler because the retailer handles the surrender. What you need to keep is the GreenPower audit certificate the retailer issues each year, plus the underlying LGC surrender IDs where those are provided.

PPA settlements are the messiest. Under a physical PPA you take title to the electricity and the LGCs, and you need to surrender the LGCs yourself. Under a virtual PPA (a financial contract-for-difference) you never take the electrons, only the LGCs, and you need to surrender them the same way. The settlement statement from the offtaker is not enough. The LGCs still need to surface in the REC Registry as retired against your entity name. We wrote a longer piece on this at power purchase agreements and carbon accounting.

The GHG Protocol Scope 2 Quality Criteria for market-based instruments

Before you count a certificate against your Scope 2, it has to pass all eight Scope 2 Quality Criteria set out in Appendix A of the Scope 2 Guidance. Most reporters have never read them. We keep a checklist inside the retirement record because they are the questions the auditor will ask.

The criteria in plain terms: the instrument conveys attribute information (technology, vintage, generator); it is the only claim to that MWh; the attributes are tracked and redeemed within the reporting period or within one year of it; the instrument is issued and redeemed as close as possible to the consumption period; it is sourced from generation within the same market boundary as the consumption; it is a contractual instrument rather than a policy artefact; the residual mix has been adjusted to avoid double-counting; and the entire chain is auditable back to the generator.

The two that trip Australian reporters most often are the geography test and the vintage test. Imported I-RECs from South-East Asia do not satisfy the geography test for Australian consumption. LGCs surrendered from a 2019 vintage against 2025 consumption fail the vintage test (which is why the GreenPower rules include a specific vintage window). Both look fine on the invoice. Both fail assurance.

How the REC Registry works and what the surrender record actually looks like

The Clean Energy Regulator runs the REC Registry as the single source of truth for LGCs and STCs. Every certificate has a unique identifier, a generation period (the year and quarter the underlying MWh was produced), a generator, a technology type, and a current status. Status transitions through created, transferred, and surrendered. Once surrendered, a certificate cannot be reused.

When you or your retailer surrenders an LGC against a voluntary claim, the registry produces a surrender confirmation. That confirmation has the certificate ID, the surrendering entity, the surrender date, a reason code, and (critically) the notation that the surrender was voluntary rather than for LRET liability. Voluntary surrender is the one that counts for market-based Scope 2. LRET compliance surrender does not.

For every MWh you want to claim as renewable under the market-based method, there needs to be a matching surrender record. Not the invoice from the retailer. Not the confirmation email. The registry record. When we designed the retirement ledger inside Carbonly, we assumed the auditor would ask to see this document during the walk-through, and we built the storage to keep it linked to the certificate row indefinitely.

What the reporter needs to track per certificate

There is a minimum data set for every certificate you claim, and if any of these fields is missing at the point of assurance, the claim is at risk. The retirement ledger in Carbonly captures the following on each row.

Field	What it is	Why the auditor cares
Certificate type	LGC, STC, GreenPower, PPA-linked LGC, I-REC, GO	Determines which quality criteria apply
Registry certificate ID	The unique identifier from the REC Registry (or equivalent)	Traceability back to the source system
Vintage year	4-digit generation year	Vintage-match test under Scope 2 Quality Criteria
Quantity retired (MWh)	Megawatt-hours covered by the certificate	Reconciles to consumption on a MWh basis
Generator / facility name	The named generator that produced the MWh	Attribute conveyance test
Facility location	State or region	Market boundary geography test
Technology type	Solar, wind, hydro, biomass, etc.	Attribute conveyance and reporting narrative
Purchase date and price	When the certificate was acquired and for how much	Internal carbon price analysis, cost tracking
Retirement date	The date the surrender was recorded in the registry	Timing test, surrender within reporting period
Retiring party	The entity name on the surrender confirmation	Exclusivity test, no double claim
Retirement reason	Voluntary Scope 2, regulatory, contractual	Only voluntary retirements count for market-based
Issuing registry	REC Registry, IREC Standard, AIB Hub, etc.	Determines applicable rules
Evidence document	The surrender confirmation PDF or equivalent	The document the auditor asks for

The retirement ledger enforces a few rules that catch common errors before they get into a report. Retirement dates cannot be in the future. Zero-MWh entries are rejected. Vintages must be a 4-digit year. And the record is append-only in practice. Once a retirement is entered, changes are for evidence attachment and note corrections, not for revising the underlying MWh.

The dual disclosure: location-based and market-based run in parallel

AASB S2 paragraph 29(a)(v) requires both the location-based Scope 2 total and the market-based Scope 2 total. You do not pick one. Both go in.

For most Australian reporters, the location-based figure uses the state grid emission factor from the DCCEEW NGA Factors workbook: 0.64 kg CO2-e per kWh in NSW, 0.78 in Victoria, 0.20 in Tasmania, and so on. Multiply consumption by the state factor and you have your location-based number.

The market-based figure starts from the same consumption data but adjusts for surrendered certificates. Every MWh backed by a valid, voluntarily surrendered LGC (or equivalent) drops out of the emissions calculation and is replaced with a zero. Everything else uses either a residual mix factor (where available) or the location-based factor as a fallback. Australia now has a residual mix factor published in the NGA workbook, which changed the market-based math meaningfully in 2025. The residual factor is higher than the grid average because the LGCs are stripped out.

The point is that these two figures should almost always diverge if you have any renewable certificates at all, and the auditor will look at the divergence and want to see the surrender ledger that justifies it. We covered the mechanics of the split in more detail at location-based vs market-based Scope 2.

How Carbonly stores REC retirement records

The retirement ledger sits alongside the emission ledger inside Carbonly. Each certificate is a row with the fields listed above, plus organisation and business-unit scoping so a multi-entity group can allocate certificates to the specific site that consumed the electricity. Certificates are linked to individual emission records through an allocation table, which is what lets one large LGC parcel cover consumption at multiple sites and still preserve the audit trail on each.

Only Owners and Admins can create, update, or delete a retirement record. Contributors and Managers can view the ledger but cannot alter it. That is deliberate. The retirement ledger is a compliance artefact, and the roles that touch it need to be tightly held. The retirement records are retained for 7 years, which exceeds the NGER Act section 22 five-year record-keeping floor and gives headroom for reasonable assurance restatement conversations.

The workflow assumed by the ledger is that a certificate is entered when it is surrendered, not when it is bought. Purchase and surrender are often separated by months, sometimes years, and the market-based claim only lands when the surrender happens. Entering certificates on purchase creates an inventory management problem the ledger is not designed to solve. Enter on surrender, and the retirement date on the record matches the date on the registry confirmation.

PPA settlement statements, the additional evidence layer

For reporters with PPAs, the ledger sits on top of the PPA settlement statements rather than replacing them. Each settlement period (monthly for most Australian PPAs) generates a statement showing MWh generated, LGCs delivered, and price settlement. Those statements feed the ledger with the LGC IDs and vintages, which then get carried forward to the surrender step.

The PPA layer adds two things the ledger needs to handle. First, LGC creation lag. A PPA generation event in October may not produce a certificate in the registry until December, and the reporter has to be careful not to double-count on the transition. Second, physical versus virtual PPAs treat the underlying electricity differently, but from a certificate-tracking perspective the surrender step is identical. The settlement statement tells you which LGCs are yours; the registry surrender confirmation proves you retired them.

The PPA settlement statement itself is not sufficient evidence for the market-based claim. The auditor will still want the registry surrender record. But it is a useful reconciliation document, and Carbonly stores it alongside the LGC records for the reporting period so both can be produced together during the walk-through.

Integration with the Auditor Workspace

The Auditor Workspace inside Carbonly gives external assurance providers direct, read-only access to the emission ledger, source documents, and (the piece that matters for this post) the retirement ledger and its attached evidence.

During an ASSA 5010 walk-through, the auditor will typically sample somewhere between 15 and 30 emission line items and trace each back to source. For electricity claimed under the market-based method, that trace includes the LGC surrender confirmation. Having the surrender PDF attached to the retirement record inside the workspace means the sample can be resolved in the tool rather than through email chains and shared drives. We built the workspace this way after mapping out where first-time reporters were losing days of preparation time during their first assurance engagement.

The Evidence Pack export bundles the retirement records for a reporting period into a single archive, with the surrender confirmations, PPA settlement statements, and GreenPower audit certificates all included and cross-referenced to the market-based Scope 2 line in the report. This is what most preparers now hand to their auditor as the starting artefact for the Scope 2 walk-through.

What Carbonly does NOT do

Honest disclosure section, because this comes up in every conversation.

We do not have a direct API integration with the REC Registry. There isn't a public one. Certificates come into the retirement ledger via CSV import or manual entry, with the registry surrender confirmation attached as an evidence document. If and when the Clean Energy Regulator opens a machine-readable interface for authorised parties, we will build to it. Until then, the workflow is upload-and-attach rather than sync.

We do not generate the surrender itself. The retirement action happens inside the registry, initiated by the certificate holder or their retailer. Carbonly records it after the fact and links it to the affected emissions. This distinction matters. The retirement ledger is a record-keeping and disclosure tool, not a trading or registry tool.

We do not run a certificate marketplace. If you want to buy LGCs, you go to a broker or your retailer. We hold the accounting side.

FAQ

Do I need to surrender LGCs to claim the location-based figure? No. Location-based Scope 2 uses the state grid emission factor and does not reference any certificates. Certificates only affect the market-based figure, which is disclosed alongside the location-based one under AASB S2. Both are required.

Can I claim rooftop solar without STCs? Yes. Behind-the-meter generation from your own rooftop system is treated as zero-emissions for Scope 2 regardless of whether STCs were created, because those kWh were never purchased from the grid. STCs are an installation-cost rebate, not a certificate-of-attribute for accounting purposes. Do not try to double-count.

What vintage year of LGC can I use against 2026 electricity consumption? Under the Scope 2 Quality Criteria vintage-match test, the certificate should be from the same year as the consumption or within a defined window. GreenPower rules use a 27-month vintage window. For voluntary Scope 2 claims outside GreenPower, sticking to the same calendar year as consumption is the safe default and the one auditors will not push back on.

How long do I need to retain the surrender records? NGER Act section 22 sets a five-year floor. AASB S2 does not set a specific retention period, but assurance restatement windows can push you longer. Carbonly retains retirement records for 7 years by default to cover both. Keep the registry confirmation PDF, not just a reference number.

Can one large LGC surrender cover multiple sites? Yes. A single surrender of, say, 5,000 LGCs can be allocated across multiple business units in the retirement ledger, provided the total allocated MWh does not exceed the surrendered quantity. The allocation table inside Carbonly is what preserves the split so each site can trace its market-based claim back to a specific portion of the surrender.

Where to start

If you are moving to market-based Scope 2 for the first time under AASB S2, the practical sequence is: pull twelve months of electricity consumption by site, pull twelve months of LGC and GreenPower purchases, list every certificate ID with vintage and MWh, and check each one against the REC Registry for surrender status. That reconciliation is the foundation. Everything else (the report, the disclosure narrative, the walk-through with the auditor) is easier once the retirement ledger matches the certificates you paid for.

Carbonly is priced per-project plus $100 per month for the platform. Reach out at hello@carbonly.ai and we can walk through the retirement ledger with your Scope 2 data.

Related reading