Limited vs reasonable assurance of emissions data
The "Assurance" line on many company pages names the firm that checked the emissions figures, such as one of the large audit firms or a certification body like SGS, Bureau Veritas, DNV or LRQA. The level of assurance tells you how much checking was done.
Limited assurance
The assurer performs mostly enquiries and analytical procedures and gives a negative-form conclusion, typically worded: "nothing has come to our attention that causes us to believe that the selected information is not prepared, in all material respects, in accordance with…". It is the most common level for sustainability data and costs much less than an audit.
Reasonable assurance
A higher level, comparable to a financial statement audit. The assurer tests controls and underlying data in depth and gives a positive opinion that the figures are fairly stated. Fewer companies obtain it, and often only for Scope 1 and 2.
| Limited | Reasonable | |
|---|---|---|
| Wording | "Nothing has come to our attention…" | "In our opinion, the information is prepared, in all material respects…" |
| Depth of work | Enquiries, analytics, limited sampling | Detailed testing of data and controls |
| Typical scope | Scope 1, 2 and often parts of Scope 3 | Usually Scope 1 and 2 |
| Cost and effort | Lower | Higher |
Standards you will see named
- ISAE 3000 (Revised): the general international standard for non-financial assurance engagements.
- ISAE 3410: assurance on greenhouse gas statements specifically.
- ISSA 5000: the IAASB's standalone standard for sustainability assurance engagements (limited and reasonable), issued in 2024.
- ISO 14064-3: verification and validation of greenhouse gas statements, common with certification bodies.
- AA1000AS v3: AccountAbility's assurance standard, which also looks at stakeholder inclusiveness.
How to read an assurance statement
- Check exactly which metrics were covered. It is often only selected indicators, not the whole report.
- Check the year: some reports carry assurance for the previous year's data only.
- Look for qualifications or emphasis-of-matter paragraphs.
Assurance requirements are spreading: the EU's CSRD starts with limited assurance, and India's BRSR Core requires independent assurance or assessment of key indicators for the largest listed companies. Related: reporting frameworks explained.
More guides
- Scope 1, 2 and 3 emissions explained
- The 15 Scope 3 categories
- Market-based vs location-based Scope 2 emissions
- What does tCO₂e mean?
- How to find a company's sustainability report and emissions data
- Sustainability reporting frameworks explained
Last reviewed: October 2026. Spotted an error? Tell us.