An empirical study of sustainability reporting assurance: current trends and new insights

Purpose: This study aims to examine trends in the global assurance practices of sustainability reports, updating and broaden the extant literature and proving new insights that could guide future research. Design/methodology/approach: The data were collected for 12,783 companies and exploratory descriptive analyses of sustainability reporting assurance practices were undertaken. Findings: The study shows that assurance growth is lagging behind the growth in sustainability reporting. It reveals that assurer switching is a common practice amongst companies. There is an increasing trend towards the use of the International Standard for Assurance Engagements 3000 by non-accounting assurers. Additionally, in terms of assurance providers, the study finds that accounting firms are dominating the market, however, engineering firms are fast increasing their share of the sustainability assurance market, whilst consulting firms’ share is decreasing. However, the switch towards consulting firms is higher than the switch towards accounting firms in the last switch period. Practical implications: Overall, the results of this study provide insights about companies’ assurance practices for regulators, assurance providers and companies interested in assuring their sustainability reports. Social implications: This study is relevant for companies’ stakeholders, including investors, to enhance their understanding of companies’ current assurance practices. Originality/value: Prior studies on the assurance practices of sustainability reports are limited in scope (concentrate on large companies) and depth (examine accounting vs non-accounting assures and consider the evolving patterns at the institutional rather than firm-level). This study presents developments and trajectories of assurance practices to inform researchers and practitioners on the global trends by bringing an updated and broader perspective on the topic.