What assurance providers ask for in a sustainability report
The evidence, documentation and controls an assurance provider typically expects to see when reviewing a sustainability report, and how to prepare before they arrive.
Assurance is an independent check of your sustainability information. Limited assurance is a lower level of work than a financial audit, but it still needs organised evidence. If you want the concepts first, read ESG assurance explained.
Where the rules stand
The CSRD requires assurance of the sustainability statement, and limited assurance is the level currently required. Under Omnibus I, the deadline for the Commission to adopt an EU limited assurance standard moved to 1 July 2027, and the audit regulators' committee (CEAOB) adopted its technical advice on 25 September 2026 (published 6 October), starting from the IAASB's ISSA 5000. Until an EU standard exists, providers work to national requirements, often based on the IAASB's ISSA 5000. Who may perform the work depends on each Member State's transposition. Check national rules.
What providers typically look at
| Area | What they tend to ask for |
|---|---|
| Scope and boundary | Which entities and sites are included, and why |
| Materiality | The method note, scores, sign-off and minutes |
| Methods | Written calculation methods and factor sources |
| Data | Source records for sampled figures |
| Controls | Who prepares, reviews and approves each figure |
| Consistency | Prior-year figures and explanations of changes |
| Estimates | Assumptions, ranges and why they are reasonable |
Evidence that is commonly requested
- Energy and fuel: invoices, meter readings, fuel card statements.
- Emissions: the inventory file, the emission factor tables with year and source, and a reconciliation to activity data.
- People data: HR system extracts reconciled to payroll.
- Safety: the accident log and investigation records.
- Policies: the signed policy, the approval date and evidence it is communicated.
- Targets and actions: board decisions, budgets and progress reports.
How to prepare
- Build an evidence index. One row per reported figure, with the source file, the owner and the date.
- Write the methods down. Anyone should be able to repeat a calculation.
- Reconcile. Totals by site should add to the group figure, and the data should agree with your accounts where they overlap.
- Control versions. Lock the data once it is reported and keep a record of changes.
- Run an internal review. Pick ten figures and trace them to source as a provider would.
- Agree the timetable early. Provide drafts and ask what format they prefer.
Common reasons for findings
- Figures that cannot be traced to a source.
- Methods that changed without explanation.
- Estimates with no stated basis.
- Boundaries that differ between sections.
Find an assurance provider
Bureau Veritas
Testing, inspection and certification group offering GHG verification and sustainability assurance.
Speeki
Singapore-based assurance, verification and certification provider with software for ESG report and management system audits.
Pangolin Associates
Australian climate consultancy covering emissions measurement, climate risk, strategy, verification and disclosure support.
TUV Rheinland
Technical services provider offering certification and auditing, including environmental and energy management system certification.
AccountAbility
Sustainability advisory firm that also develops the AA1000 standards on stakeholder engagement, assurance and accountability.
Microfinanza Rating
Italian rating agency providing ESG assessments, second party opinions and impact assessments for financial institutions.
Ordered by verified reviews and relevance. Listings are never ranked by payment. See all 35 providers
Also see how to choose an ESG consultant and our checklists.
Official sources
This guide is general information, not legal, tax or investment advice. Rules change; check the official sources and talk to an adviser before you rely on it.
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