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Scope 3 is Changing: What the GHG Protocol's Phase 1 Update Means for AASB S2 Reporters

Scope 3 is Changing: What the GHG Protocol's Phase 1 Update Means for AASB S2 Reporters
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Written by:
Trace Insights
Publish Date:
Jun 2026
Topic Tag:
Sustainability

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The GHG Protocol's Corporate Value Chain (Scope 3) Accounting and Reporting Standard is being revised for the first time since 2011. It is the world's most widely used framework for measuring value chain emissions and the methodology AASB S2 explicitly mandates. On 31 March 2026, the GHG Protocol published its Phase 1 Progress Update. A draft, not a final standard, but the clearest signal yet of where Scope 3 reporting is headed. A public consultation draft is expected mid-2026, with the final revised standard targeted for late 2027 and likely to take effect from 2028.

The proposed changes include a 95% inclusion rule, mandatory disaggregation of Scope 3 emissions by data quality tier, and new third-party verification labelling. For Australian AASB S2 reporters, the Phase 1 update is not an abstract overseas development, it is a direct preview of how Scope 3 disclosure is likely to change.

What's changing in the GHG Protocol Scope 3 Standard?

The 95% inclusion rule: quantifying what you exclude

Historically firms have been given the autonomy of deciding what they include and exclude from Scope 3 reporting, allowing emissions that were deemed immaterial or outside of their direct control to be excluded.

The key proposal is that companies would need to account for at least 95% of required Scope 3 emissions with exclusions capped at 5% and quantitatively justified. In practice, this means companies must estimate 100% of their required Scope 3 emissions in order to demonstrate that what they exclude sits within the 5% cap — a qualitative description of materiality will no longer be sufficient. 

The revised approach ensures that all activities attributable to the firm's business will be accounted for in the scope 3 inventory with the exclusion for minor emissions. This gives more emphasis on “customers” of emissions to play their role in decarbonisation. 

Requiring companies to report at least 95% of their scope 3 emissions ensures more complete, consistent, and transparent reporting by setting a clear threshold for what can be excluded.

Data quality tiers: primary, secondary and spend-based

Another major change is that Scope 3 emissions would need to be disaggregated by data quality for each category, with the goal of improving transparency and comparability. The Phase 1 update is consulting on two options that are structured around: 

  • Data specificity (measured or specific, other, spend-based) 
  • Data source and calculation method (primary, secondary, spend-based) 

Both share the same direction: primary or measured data at the top, spend-based at the bottom, with an "unclassified" catch-all for emissions a company is unable to disaggregate.

Although this aims to improve how companies collate and report data, the practical effect is that spend-based estimates which are currently the default for most Australian reporters will be publicly labelled as the lowest-quality tier, creating visible pressure to shift high-impact categories onto primary or specific supplier data. This is a significant challenge in practice since more specific supplier data largely doesn't exist in the market today, and where it does, it isn't generally accessible to reporters.

The "unclassified" tier is intended as a catch-all for emissions a company cannot disaggregate, but without clear disclosure rules around its use, it risks becoming a loophole for firms to choose not to classify their data. This isn't recommended, even lower-tier classified data, including spend-based, is more useful to assurers and investors than an unclassified aggregate that hides how the number was built.

Verification labelling: verified, partially verified, not verified

A separate proposal would require companies to state whether their reported Scope 3 data is verified by a third party, using labels such as verified, partially verified, or not verified. In practice, that would push Scope 3 reporting away from a single aggregate disclosure and toward a more layered disclosure structure that shows both data quality and assurance status.

What does this mean for Australian firms?

The 95% rule changes the conversation about materiality

The 95% rule will reshape how firms approach materiality. Under AASB S2 today, many Australian firms have leaned on qualitative relevance assessments to scope down their Scope 3 reporting. A prescriptive 95% inclusion threshold narrows that flexibility considerably. Reported Scope 3 totals are likely to rise across the ASX as companies include previously excluded categories, and base year recalculations should be expected when the revised standard takes effect. The first priority for many firms will be reviewing whether current exclusions rely on assumptions that may not hold under the revised framework.

Today’s investments in data architecture will pay dividends later

The disaggregation requirement means emissions systems need to track how each data point was calculated, not just what the number is. Spreadsheet-based approaches will struggle to meet the evidentiary burden, particularly as limited assurance moves toward reasonable assurance by 1 July 2030. Those putting in the work today to understand, map and properly tag their Scope 3 emissions will be well positioned when expectations tighten.

Supplier engagement shifts from a procurement task to a strategic capability Limiting the use of corporate-average supplier data where a supplier's entire business emissions is applied to estimate the firm's purchased goods and services combined with the push toward primary, supplier-specific data, means procurement teams must build supplier engagement into onboarding, contracts, and Tier 1 relationships. For Australian firms with concentrated supplier bases or strong commercial leverage, this is an opportunity to shape supplier decarbonisation rather than respond to it.

How the revisions interact with AASB S2

AASB S2 explicitly mandates the GHG Protocol as the measurement methodology for Scope 3, which means changes to the Protocol flow directly through to what conformant disclosure looks like under Australia's mandatory climate reporting regime. The direction of travel matters now, even though the standard itself is not expected to take effect until 2028 or later. There is a recent precedent for how this is likely to play out. In December 2025, the AASB issued amendments to AASB S2 that copied a set of changes the ISSB had just made to IFRS S2. Those amendments take effect from 1 January 2027, with early adoption optional. That same pattern of waiting for international change, mirroring it locally, and allowing firms to opt in early is the most likely template for how Australia will pick up the Phase 1 revisions.

Why Australian reporters should act now, not in 2028

The timing actually works in Australia's favour. Group 1 entities are already reporting under AASB S2, and Group 2 and Group 3 reporters are still building their systems. Companies preparing now have the opportunity to design their data architecture, supplier engagement programs, and governance processes against the revised standard from the outset, rather than retrofitting later when the rules are locked in. Executive teams should treat the current update as an early signal to test assumptions before the final standard is issued, rather than waiting for the consultation draft to land.

What companies should be doing now

For reporters yet to publish their first-year report, the focus should be on establishing robust, supportable reporting foundations that will hold up under tighter rules. For second-year reporters, maturing understanding and measurement of Scope 3 emissions is the next step. 

Regardless of your group, critical actions are worth attention now:

  1. Identify who owns  Scope 3 boundary-setting, measurement, and reporting decisions
  2. Understand current Scope 3 exclusions against the proposed 95% threshold and quantify what needs to be expanded
  3. Document which categories rely on spend-based versus supplier-specific data

Where .Carbon fits

Trace built .Carbon, our integrated carbon emissions measurement tool and sustainability reporting tool for Australian organisations navigating AASB S2. It gives practitioners Scope 1, 2, and 3 quantification, scenario modelling, AASB S2-aligned disclosure scaffolding, and progress tracking against targets. With the Phase 1 revisions focusing on completeness, data-quality and verification expectations, now is the time to move away from spreadsheets and into a structure that is sustainable.

Get your Scope 3 reporting AASB S2-ready with Trace

Trace helps Australian firms prepare Scope 3 emissions disclosures that are structured for assurance under ASSA 5010, aligned to AASB S2 and the GHG Protocol, before the Phase 1 revisions take effect.

We can help you:

  • Quantify Scope 1, 2 and 3 emissions 
  • Build AASB S2-aligned disclosures with the data tagging needed for limited and reasonable assurance
  • Assess whether your current exclusions and materiality assumptions will hold under the revised standard

Book a 30-minute .Carbon walkthrough to see how we can support your reporting requirements.

Ready to turn insight into action?

We help organisations transform ideas into measurable results with strategies that work in the real world. Let’s talk about how we can solve your most complex supply chain challenges.

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