Does the rhetoric art in sustainability reports obstruct the assurance practice?

PurposeThis paper aims to investigate the relationship between the readability of sustainability reports and assurance provider effort, captured by assurance delay and the moderating effect of the assurance provider.Design/methodology/approachThis sample consists of companies operating in sustainability sensitive industries from 39 countries for the period that covers the years 2016–2018.FindingsThe results show that poor sustainability reporting readability is associated with longer assurance delays. Indeed, assurance providers spend more effort assuring clients when sustainability reports are less readable, as shown by long assurance delay. In addition, increases in assurance delay associated with poor sustainability reporting readability are driven by accounting assurance providers. These results hold after controlling for endogeneity using Heckman's (1979) analysis and other measures of assurance delay readability used in prior literature. By checking the specialization of assurance provider partners and setting aside dominant countries, the authors provide insight into the impact of assurance provider specialization on the association between sustainability report readability and assurance provider effort measured by assurance delay and thus, lending further confidence to the strength of the study’s main findings.Research limitations/implicationsThis research provides preliminary evidence on the relationship between sustainability reporting readability and assurance delay as well as the influence of accounting assurance providers.Practical implicationsSustainability assurance practice is viewed as a tool to add or enhance credibility. This study could be considered as another step into driving the standardization of sustainability reporting practice internationally.Originality/valueThis is the first investigation conducted in the sustainability literature on the assurance provider's response to the readability of sustainability reports.