1. What Is “Assurance” in ESG/Sustainability Reporting? Assurance provides external verification of non‑financial (ESG) data — confirming that the information in a sustainability or climate report is reliable, consistent, and prepared in accordance with recognized standards such as: ISAE 3000 (Revised) – International Standard on Assurance Engagements AA1000 AS v3 – AccountAbility Assurance Standard CSRD / ESRS (EU) – which will mandate limited or reasonable assurance