ISSA 5000 case study: Estimates and forward-looking information
In partnership with ACCA, this case study provides illustrative limited and reasonable assurance procedures for GHG emissions disclosures under ISSA 5000.
In brief
- Explores the assurance challenges of estimates and forward-looking information.
- Illustrates practical judgement points through a detailed case study.
- Outlines key ISSA 5000 requirements for limited and reasonable assurance.
Estimates and forward‑looking information are central to sustainability reporting, but they also bring uncertainty, assumptions and potential bias. This practical case study outlines how practitioners can apply International Standard on Sustainability Assurance 5000 General Requirements for Sustainability Assurance Engagements (ISSA 5000) to this challenging area, focusing on what assurance can do in practice and how to communicate inherent limitations clearly.
Expanding on the ABC plc scenario introduced in the first guide of this series focusing on materiality, this case study:
- Outlines the applicable ISSA 5000 requirements and the professional judgement points involved in assuring disclosures of:
- an estimate (market-based Scope 2 GHG emissions); and
- forward-looking information (net zero target for Scope 1 and Scope 2 GHG emissions).
- Demonstrates the differentiation between limited assurance (disclosure-level) and reasonable assurance (assertion-level) procedures.
- Illustrates practitioner considerations when responding to risks of material misstatement arising from methodology changes, estimation uncertainty and potential management bias.
- Supports practitioners in evaluating the relevance and reliability of evidence, including internal data, external sources and expert input.
- Provides guidance on evaluating whether uncertainty is communicated clearly and proportionately to intended users in both the sustainability report and the assurance report.
- Reinforces the importance of obtaining sufficient and appropriate evidence, maintaining reliable documentation, and clearly linking professional judgements to the evidence obtaining approach and evaluation of misstatements.
By bringing together key ISSA 5000 requirements and practical illustrations, this publication aims to promote a consistent and proportionate approach to assurance in this evolving area. It is intended to assist assurance practitioners, preparers and users in understanding what assurance over estimates and forward-looking information can and cannot provide.
