Limited Assurance
Limited assurance is the lower of two assurance levels used by auditors to examine CSRD sustainability disclosures, resulting in a negatively worded conclusion that nothing material has come to the auditor's attention.
Limited assurance describes the level of confidence with which the sustainability assurance provider examines the disclosures required under the Corporate Sustainability Reporting Directive (CSRD). At this level the auditor mainly performs analytical procedures and inquiries and does not carry out the full extent of detailed substantive testing. The outcome is a negatively (limited) worded conclusion: the auditor states that, based on the work performed, nothing has come to their attention that causes them to believe the sustainability report does not comply, in all material respects, with the European Sustainability Reporting Standards (ESRS).
Limited assurance must be distinguished from reasonable assurance, which requires a higher level of confidence and a positively worded conclusion. The CSRD provides that the assurance of sustainability disclosures starts at the limited level, with the option of a later transition to reasonable assurance. The European Commission was tasked with adopting corresponding assurance standards; in Germany the assurance obligation is anchored in the Commercial Code (HGB) and audit law. Until EU-wide standards are adopted, national requirements apply together with the IAASB standards, in particular ISSA 5000 for sustainability assurance engagements.
For reporting companies, limited assurance means that the internal processes, data sources and controls around the ESRS data points must be documented in an audit-proof manner. Even though the depth of testing is lower than under reasonable assurance, the auditor expects traceable derivations, consistent methods for estimates and a robust link between the materiality assessment, data collection and reported figures. A weak data basis can lead to scope limitations, follow-up questions or, in extreme cases, a qualified assurance conclusion.
Legal Basis
Art. 26a of the EU Audit Directive 2006/43/EC (introduced by the CSRD Directive (EU) 2022/2464); ISSA 5000 (IAASB); Sections 324b et seq. HGB
Practical Example
A mid-sized mechanical engineering company prepares its first CSRD-compliant sustainability report under the ESRS. The sustainability officer prepares for the limited assurance engagement by documenting, for each material data point - such as Scope 1, 2 and 3 emissions and own-workforce metrics - the source file, the calculation method used and the responsible owners. When the auditor notices an unusual fluctuation in the energy figures during analytical review and asks about it, she can immediately substantiate the one-off effect (a plant expansion). This allows the company to avoid scope limitations and to receive an unqualified limited assurance conclusion.