AASB S2 Climate-Related Disclosures

What is AASB S2?

AASB S2 Climate-related Disclosures is Australia's mandatory climate reporting standard, issued by the Australian Accounting Standards Board and aligned with the ISSB's IFRS S2. It requires large Australian entities to disclose climate-related risks and opportunities across four areas: governance, strategy, risk management, and metrics and targets.

The metrics and targets component is where emissions data matters. Entities must disclose Scope 1, Scope 2, and (where material) Scope 3 greenhouse gas emissions, calculated using the government-mandated NGA emission factors published by DCCEEW.

AASB S2 is phased by group:

• Group 1 (largest entities, NGER reporters) — mandatory from 1 January 2025
• Group 2 (~3,000 entities, revenue >AU$200M or assets >AU$500M) — mandatory from 1 July 2026
• Group 3 (remaining large entities) — mandatory from 1 July 2027

Limited assurance applies from Year 1. That means your emissions calculations need a defensible audit trail from the first reporting period, not a retrospective cleanup.

What are NGA emission factors and why do they matter?

NGA (National Greenhouse Accounts) emission factors are the government-mandated conversion rates that translate energy consumption and activity data into CO2-equivalent emissions. Published annually by DCCEEW, they cover electricity consumption by state and territory, stationary combustion fuels (natural gas, diesel, LPG, coal), and transport fuels.

For AASB S2 reporting, you must use NGA Factors — not third-party estimates, not vendor-supplied approximations. Using the wrong factor, or the right factor from the wrong year, produces a non-compliant disclosure. The version and publication year of the factor used must be traceable back to the original DCCEEW workbook.

Current electricity emission factors by state (NGA 2025 workbook):

These factors update annually. The version and publication reference that was current when your calculation ran is what your auditor needs to see.

The problem with spreadsheet-based calculations

Most teams start their AASB S2 reporting process by downloading the DCCEEW NGA Factors workbook and manually referencing the relevant rows. This works for a single calculation on a single date. It breaks down across three dimensions:

• Version provenance: A downloaded spreadsheet has no timestamp and no version reference embedded in the calculation. If DCCEEW updates the workbook mid-year and you download a new copy, there is no record of which version each historical calculation used.
• Consistency across facilities: Multi-site operations with separate teams producing emissions data in parallel frequently end up with different workbook versions applied to different sites, which creates a reconciliation problem at consolidation time.
• Audit trail: Limited assurance under AASB S2 requires your auditor to be able to trace each emissions figure back to a specific factor, from a specific published source, at a specific point in time. A cell reference in a spreadsheet does not satisfy that requirement.

How the API solves it

The NGA Emission Factors API returns the correct factor for any fuel type, state, and year — with the DCCEEW workbook version and publication reference embedded in every response. The calculation can always be traced back to exactly which published workbook it used, regardless of when you run it.

Quick example — Scope 2 electricity factor for NSW

import requests

resp = requests.get(
    "https://api.techcompass.com.au/v1/au/climate/nga-factors",
    params={"state": "NSW", "fuel_type": "electricity", "year": 2025},
    headers={"Authorization": "ApiKey tc_live_<your_key>"}
)

result = resp.json()["data"]["results"][0]
print(result["emission_factor"])        # 0.64
print(result["unit"])                   # "kg CO2-e/kWh"
print(result["publication_reference"])  # "National Greenhouse Accounts Factors 2025"
print(result["workbook_version"])       # "2025"

# The data_lineage block is your audit trail
lineage = resp.json()["data_lineage"]
print(lineage["source"])                # "DCCEEW National Greenhouse Accounts Factors 2025"
print(lineage["retrieved_at"])          # "2026-09-19T10:00:00Z"

Store the data_lineage block alongside each emissions calculation and you have the provenance record your auditor needs.

Which plan you need

Further reading

• AASB S2 Group 2 is mandatory now — what a downloaded NGA Factors spreadsheet doesn't give your auditor
• AASB S2: How to find out who has to report and when
• AASB S2 Group 2 mandatory reporting checklist 2026 — 10 steps
• NGA Factors 2026: AASB S2 audit trail requirements and version history

Frequently asked questions