Glossary›Emissions accounting and measurement›Primary vs secondary data
Glossary term
Cluster D · D16
Tier 1
Primary vs secondary data
Definition
Primary data is obtained directly from activities within the entity’s own value chain, such as a supplier’s own measured figure or the entity’s own meter readings. Secondary data comes from published averages, industry databases or modelled datasets. AASB S2 requires primary data to be prioritised, all else being equal, because it better represents the entity’s actual activity.
AASB S2 Appendix B
· paragraphs B46 to B49 ·
In force
On this page
In practice
The standard defines this precisely and the definition is narrower than the everyday use of the words. Appendix B paragraph B46 frames it as data obtained directly from specific activities within the entity’s value chain (primary) versus data not obtained directly from those activities (secondary), or a combination. Paragraph B47 requires the entity to prioritise primary data, all else being equal, because it is more likely to be representative of the entity’s actual value chain activity.
Paragraph B48 gives the examples, and they are broader than reporters expect. Primary data includes data provided by suppliers or other entities in the value chain relating to specific activities in the entity’s value chain. It can be collected internally through the entity’s own records, or externally from suppliers and other value chain partners: supplier-specific emission factors for purchased goods or services are named explicitly. Meter readings and utility bills are given as examples.
Two implications that change how a controller approaches this.
Your own utility bills are primary data. People assume primary means supplier-engagement work. Your electricity invoices and fuel card statements are primary data for Scope 2 and Scope 1 respectively, and most entities already hold them. The primary data problem is a Scope 3 problem, not an inventory-wide one.
A supplier-specific emission factor is primary data. This is the highest-leverage item in a Scope 3 programme. Asking your ten largest suppliers by spend for their product carbon footprint converts the largest chunk of your Category 1 from secondary to primary in one exercise, and it is a procurement conversation rather than a measurement project.
The trap is credibility. Primary is prioritised by the standard because it better represents the entity’s activity, not because it is automatically more reliable. A supplier figure that arrives as a single number with no method, no boundary and no verification is primary and weak. A well-documented published average is secondary and strong. The standard’s paragraph B40 characteristics resolve this: verification is a separate characteristic from source, and both are in play.
For a private Australian business the practical position is that a first inventory will be overwhelmingly secondary on Scope 3 and overwhelmingly primary on Scope 1 and 2, and that is normal and disclosable. What is not defensible is a second or third inventory with no movement on the categories the entity identified as material.
What the assurer does with it
For primary data the assurer tests provenance: who produced it, from what, and can they substantiate it. Supplier-provided figures get treated as third-party information rather than as source documents, because the entity did not create them and cannot vouch for the process behind them. The assurer will ask whether the supplier’s figure has been assured by anyone, and an unassured supplier figure is not rejected but is weighted accordingly.
For secondary data the test is source and applicability. They confirm the dataset is named with an edition, that the classification applied to the entity’s activity is reasonable, and that the same dataset was used consistently.
They accept primary data accompanied by the supplier’s stated method and boundary, and secondary data traced to a cited dataset and edition with a documented mapping. They reject a supplier figure with no method statement presented as a measured quantity, a shift from secondary to primary between periods presented as an emissions reduction, and a classification of internally modelled data as primary: a model the entity built is an estimate, not data obtained from an activity.
That third one is worth dwelling on. Entities sometimes label their own estimates as primary on the reasoning that they generated them in-house. Paragraph B46 turns on whether the data was obtained directly from specific activities in the value chain, not on who typed it.
Commonly confused with
Measurement versus estimation, which is a different axis. Primary data can be estimated and secondary data can be measured. Primary versus secondary asks where the data came from; measurement versus estimation asks how the number was derived.
Sources
1
2
Corporate Value Chain (Scope 3) Accounting and Reporting Standard, full text
GHG Protocol
Review status
Review required
Last reviewed
15 September 2026
Editorial pass, unsigned
Reviewer required
Carbon accounting specialist
Next scheduled review
1 July 2027
Part of
Cluster D, Emissions accounting and measurement
49 terms from the head term carbon accounting down to individual Scope 3 categories and the mechanics of factors, boundaries and data quality. The largest cluster in the glossary.
Related terms
The four-characteristic framework this axis is one part of
What fills the gap where primary data cannot be obtained
The programme that converts secondary Scope 3 into primary
Related questions
Our suppliers will not give us emissions data. What do we do?
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You estimate, and you disclose that you estimated. Nothing in AASB S2 requires primary supplier data, because the standard works on information that is reasonable and supportable and available without undue cost or effort. Rank suppliers by estimated emissions, engage the top of that list, and leave the tail on a documented spend-based method.
What is the difference between spend-based and activity-based, and which does the auditor prefer?
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Activity-based uses physical quantities such as litres or kilowatt hours, while spend-based applies a factor to dollars spent. Activity-based is more accurate and easier to evidence. An assurance practitioner has no preference in principle: they test whether the method you chose is appropriate, disclosed, and applied consistently.
Can we estimate Scope 3 and still pass assurance?
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Yes. Estimates are expected in Scope 3 and are not a problem for assurance in themselves, because what fails is an undocumented estimate. The practitioner tests whether the method is appropriate and disclosed, the inputs are traceable, the application is consistent, and the estimation uncertainty is described honestly.
Other terms in this cluster
Primary vs secondary data