The Auditor Workspace: Giving Your ASSA 5010...

The first assurance walk-through most Group 1 sustainability teams sat through last year followed the same pattern. The auditor sent a sample list. The sample list came back to the sustainability lead. The sustainability lead pulled up SharePoint, hunted for the underlying utility bill, dug into a spreadsheet, screenshot the calculation, and emailed it back. Then the auditor picked ten more records. Then ten more.

Reasonable assurance makes this worse. Group 1 reporters step up to reasonable assurance on Scope 1 and Scope 2 from financial years starting 1 July 2026 under the AUASB's phasing plan for ASSA 5010. Reasonable assurance is not a bigger version of limited assurance. It is a different assurance opinion, and the walk-through evidence bar climbs with it.

The Auditor Workspace is our answer to that. It is a dedicated role inside Carbonly built for the assurance provider. They log in themselves, sample any locked or submitted period, and generate the Evidence Pack without a single email to the sustainability team.

Why the assurance conversation is changing under reasonable assurance

ASSA 5010 (Australian Standard on Sustainability Assurance) is the standard the AUASB issued for AASB S2 climate disclosures. It aligns with IAASB's ISAE 3410 (Assurance Engagements on Greenhouse Gas Statements) so a report that stands up under one usually stands up under the other.

The phasing schedule matters. Group 1 entities under AASB S2 started with limited assurance on Scope 1 and 2 for financial years beginning 1 January 2025. Reasonable assurance on those same scopes kicks in for financial years starting 1 July 2026. Scope 3 (where categories are disclosed) moves to limited assurance later, and reasonable assurance later still. That is the AUASB pathway as published.

Reasonable assurance requires the auditor to obtain "sufficient appropriate evidence" to reduce assurance risk to an acceptably low level. In practice that means more samples, more tracing, more inquiry, and a much closer look at internal controls over the emissions calculation. If your evidence lives in a folder called Q2_utility_bills_FINAL_v3, that's a controls finding before the auditor has even opened the file.

The Auditor Workspace exists because we do not think reasonable assurance is a documentation exercise. It is a control test, and the control being tested is your ability to prove any single number in your disclosure back to a source document without anyone touching a spreadsheet.

What the Auditor Workspace actually is

It is a first-class role inside Carbonly, separate from the operational roles. The Auditor role does one thing well: it lets an external or internal assurance provider log in with read-only credentials, see everything they need, and change nothing.

Three properties define it.

First, scope-limited access. The Auditor sees reporting periods in the locked, submitted, or archived states. Open periods (where data is still being ingested) are hidden by default because unfinished data is not something a walk-through is designed to test. The walk-through tests the disclosure as prepared, not the data pipeline mid-flight.

Second, no mutation rights. There is no button in the workspace that writes to the emission ledger. The Auditor cannot re-run extractions, cannot alter factor selections, cannot re-classify a record. If they see something that looks wrong, the response is an attestation entry with an issue flag, not an edit.

Third, provenance surfaced everywhere. Every emission record in the workspace comes with its source document one click away, the reviewer who confirmed it, the timestamp of the confirmation, and the exact factor library entry (with edition year) that was applied.

What the Auditor sees when they log in

The workspace opens on the reporting period selector. Only periods in the correct lifecycle state show up.

The reporting period lifecycle in Carbonly runs open, locked, submitted, archived. Open is the working state, where data flows in and the sustainability team reviews it. Locked freezes the period for internal sign-off. Submitted marks that the disclosure has been filed with the regulator or published in the annual report. Archived closes the loop and moves the period into the long-term retention window (seven years, longer than the five years the NGER Act requires).

Once inside a period, the workspace shows four surfaces the auditor cares about.

The typed audit event stream is the first. Every state change in the ledger emits a typed event. Emission record created. Source document uploaded. Factor selected. Record confirmed by reviewer. Period locked. Period submitted. Restatement opened. Each event kind has a stable schema so an auditor can filter, sort, and export without reconstructing meaning from freeform text.

The source document library is the second. Every emission record is indexed to the file it came from, whether that's the actual PDF utility bill, the scanned fuel docket, the CSV row, or the Excel sheet. Clicking the record opens the source. The document is the same file the AI document engine extracted from originally, not a screenshot or a re-typed transcription.

The factor version stamp is the third. Every emission calculation carries the exact NGA edition (2024, 2025, and so on) and the exact factor identifier used. If the NGA workbook publishes a revision, existing records stay pinned to the version applied at the time. The workspace shows the auditor exactly which edition was used per record. This helps support the measurement approach disclosures in AASB S2 paragraph 29(a).

The attestation register is the fourth. This is where the auditor documents their walk-through outcomes.

The walk-through workflow, sampling to source in one click

Here is what a walk-through of a diesel emission record looks like in the workspace.

The auditor selects a reporting period. They open the emissions ledger filtered to Scope 1 mobile combustion. They pick a random record, say a 2,340-litre diesel entry from a construction fleet on 14 March. One click renders the source: the fuel docket PDF, with the litres, the date, the site, and the supplier all visible on the extracted document.

Beside the document, the workspace shows the reviewer who confirmed the extraction, the timestamp of the confirmation, and the factor entry (NGA 2025 diesel, mobile source, road transport) with its emission factor and units. The audit event chain for that record is one tab away: created, extracted, reviewed, confirmed, locked. Every event carries an actor and a timestamp.

The auditor now has enough to document the sample. They open the attestation register and record the outcome. If the walk-through is clean, that's a passed sample. If they have a query, they open an attestation with an issue flag. The sustainability team sees the flag in their own view but cannot resolve it silently, the audit event stream captures the flag and any subsequent response.

That whole loop, sample to source to attestation, is a short exercise instead of a multi-day evidence chase. Multiply that across the sample sizes reasonable assurance drives and the compression compounds fast.

The Evidence Pack export

The Evidence Pack is the one-click export the auditor uses when they want to take the trail offline (or when the engagement partner or engagement quality reviewer wants a copy for their own file).

It is a single ZIP. Inside:

Every emission record in the selected reporting period, exported as structured data with all provenance fields. Every source document (PDF, image, spreadsheet row export) linked to the records that reference it. The complete audit event chain for each record. The factor version log covering every NGA edition, EPD entry, and custom factor applied during the period. The restatement register, if any prior-period corrections have been logged.

The export is designed to support ASSA 5010 and ISAE 3410 engagements. It is not a submission format for any regulator, and it is not a replacement for the auditor's own working papers. It is the ledger and its provenance, in a form the auditor's file can consume.

Two things we will not claim. The Evidence Pack does not push into ASIC audit tools directly, and it does not integrate with CAANZ or IAASB submission portals. Those are workflow choices the audit firm owns. The Pack gives them the underlying evidence in a portable format, and the firm decides where it goes from there.

The auditor attestation flow

The attestation register is where the assurance provider formally records what they tested and what they concluded.

Each attestation captures the sampled record (or the population if it is a summary test), the walk-through evidence reviewed, the auditor's finding (clean, exception, or open query), and the auditor's identity. Attestations are org-scoped and cross-org isolated, so an assurance provider working on two separate Carbonly workspaces cannot see across engagements.

Attestations are immutable once submitted. They can be superseded (a later attestation can point back to an earlier one), but they cannot be silently edited or deleted.

The register is the primary interface for the assurance engagement, and it produces a chronological record of every walk-through test the auditor ran during the period. That record travels with the Evidence Pack export.

How this compresses the internal walk-through preparation

The internal cost of assurance is where most sustainability teams get blindsided. The disclosure cost is one thing. The cost of supporting the auditor's walk-through is another, and it is almost always underestimated in the first year.

We could not find a published benchmark for internal walk-through support time, but for a mid-size reporter it draws on the sustainability lead, the finance analyst who owns utility invoices, and often a third team member from operations. Limited assurance asks for less, but the load is still meaningful.

The Auditor Workspace does not remove that work entirely. Somebody still needs to answer the auditor's judgment questions about materiality, boundaries, and methodology. What it removes is the evidence retrieval load. When the auditor can sample and trace without emailing the sustainability team, that time shrinks toward the hours needed for judgment discussions only.

We're not going to pretend we've measured the exact reduction across a population of reporters yet, because we haven't. What we do know is that the mechanical part of the walk-through, the sample, trace, evidence email, screenshot cycle, is the part the workspace eliminates, and in our own reporting experience that is the worst part.

What this means for the sustainability team

Less time hunting evidence. More time on the parts of the disclosure that need actual judgment.

The pattern we designed for is the sustainability lead spending their assurance week on the qualitative sections of AASB S2, on materiality documentation, on transition plan narrative, on the Basis of Preparation. Not on retrieving a March fuel docket for the seventh time.

There is a secondary benefit. Because the auditor is working from the same live ledger the sustainability team uses year-round, there is no export-import gap where evidence gets translated into a walk-through pack and something is lost in translation. What the auditor sees is what the ledger says. That removes a class of "I sent you the wrong version" incidents.

Consultant use case

External assurance in Australia is mostly delivered by large and mid-tier audit firms and specialist climate practices.

Consultants leading the engagement can be provisioned as external Auditor role users on the customer's workspace. They log in from their own credentials, tied to their own firm, and their attestations are stamped with their identity for the audit file. Nothing on the customer's side changes. Nothing on the consultant's side needs to be built by their IT.

We think of consultants as buyers, not competitors. A consulting practice that plugs Carbonly into its assurance workflow gets to run walk-through tests across every client engagement without maintaining bespoke evidence infrastructure per client. The Auditor Workspace is the shared surface. The consultant's judgment, methodology, and firm-level review controls remain theirs.

For consulting firms running preparer-side engagements as well as assurance-side (with the appropriate independence walls), the same organisation-scoped access model applies. Preparers get Contributor or Manager roles, assurance providers get Auditor role, and the RBAC prevents accidental crossover.

FAQ

Does the Auditor Workspace change access to internal data?

No. The Auditor role is read-only and scope-limited to locked, submitted, or archived reporting periods. It cannot see open periods, cannot see draft records, and cannot modify anything. The workspace is a view over the same ledger the operational team uses, filtered to what the assurance standard treats as in-scope.

What is included in the Evidence Pack ZIP?

Every emission record in the selected period with full provenance metadata, every source document referenced by those records, the complete typed audit event chain, the factor version log, and the restatement register. It is designed to sit in an audit working paper file as evidence, not to be resubmitted to a regulator.

Which frameworks is the Evidence Pack designed for?

ASSA 5010 (Australian Standard on Sustainability Assurance) and ISAE 3410 (International Standard on Assurance Engagements on Greenhouse Gas Statements). Both standards share the same underlying evidence philosophy, and the Pack is built to serve both. The underlying data also feeds NGER audits under the NGER Determination and internal assurance for GHG Protocol reporting, but the primary design target is ASSA 5010.

How does the auditor attestation register work?

The register captures each walk-through test the auditor runs. Each attestation records the sampled record or population, the evidence reviewed, the auditor's finding (clean, exception, or open query), and the auditor's identity. Attestations are immutable once submitted, can be superseded by later attestations, and are org-scoped so multiple assurance engagements on different Carbonly workspaces stay isolated. The register exports with the Evidence Pack.

Can the auditor make changes to the ledger?

No. The Auditor role has no write path into the emission ledger, the factor library, the reporting period configuration, or any other operational surface. If the auditor finds something they think is wrong, the response is an attestation with an issue flag, which the sustainability team then addresses in their own workflow. That flag becomes part of the audit event chain. There is no silent correction path.

Where to start

If reasonable assurance on Scope 1 and 2 lands on your desk from July 2026, the question is not whether you'll get through it. The question is how much walk-through preparation your team will absorb, and whether your evidence is going to hold up under a reasonable assurance sampling plan or a limited assurance one.

Pricing is per project with a $100 per month workspace minimum. The Auditor role sits inside the workspace and the Evidence Pack export is included, not a paid add-on. Reach us at hello@carbonly.ai and we can walk you through what a walk-through actually looks like from the assurance provider's side of the screen.

The Auditor Workspace: Giving Your ASSA 5010 Assurance Team a Self-Service Walk-Through