Limited Assurance

Limited assurance is a level of independent verification in which an assurer performs enough work to conclude that nothing suggests the reported information is materially misstated. It gives a moderate level of confidence, lower than reasonable assurance, and the conclusion is worded negatively (“nothing has come to our attention”) rather than as a positive opinion that the information is correct.

The two levels differ in the depth of the work:

• Limited assurance. Relies mainly on enquiries, analytical procedures and a review of supporting evidence, with less testing of the underlying data.
• Reasonable assurance. Involves more extensive testing and results in a positive opinion that the information is fairly stated in all material respects.

This makes limited assurance faster and less costly, which is why it is the usual starting point for sustainability and emissions reporting. It is also the level required for sustainability reporting under the Corporate Sustainability Reporting Directive (CSRD). Assurers work to standards such as ISSA 5000, the International Standard on Sustainability Assurance issued by the International Auditing and Assurance Standards Board (IAASB). The standard covers both assurance levels.

For example, a manufacturer might ask an independent assurer to carry out a limited assurance review of its Scope 1, 2 and 3 emissions figures. The review covers the methodology, the emission factors and a sample of the source data. The assurer’s conclusion addresses whether anything suggests the figures are materially misstated.

Limited assurance is often the first level of assurance a business meets, and much of the preparation also applies to reasonable assurance: a documented methodology, traceable source data and consistent emission factors. Knowing how the two levels differ helps businesses plan for verification early. A closer comparison, including the standards assurers work to, is covered in limited vs reasonable assurance.