Sustainability assurance quality and board gender diversity: moderating role of assurance level and provider type on the extent of assurance procedures

Purpose This study aims to investigate the relationship between board gender diversity and the choice of assurance procedures used in sustainability assurance engagements. It also examines whether this relationship is dependent on the type of assurer and if it is particularly strong in reasonable assurance compared to limited assurance engagements. The concept of managerial capture is used to guide the analysis. Design/methodology/approach This study uses a sample of Global Fortune 500 firms. Data on sustainability assurance procedures and related variables were manually collected from sustainability reports, while financial data were obtained from the Refinitiv Eikon database. The study uses ordinary least square estimation model with fixed effects, a difference-in-difference research design and the two-stage Instrumental variable method to analyse the data set. Findings The findings of this study reveal that an increase in board gender diversity is associated with the use of a broader range of sustainability assurance procedures. This relationship is stronger when the assurers are accountants. Moreover, when sustainability assurance requires reasonable assurance, its interaction with board gender diversity results in the use of a broader range of sustainability assurance procedures. Practical implications The findings provide policymakers with a better understanding of the complementary synergies of corporate governance and assurance practitioner attributes that can be exploited for high-quality sustainability assurance engagements. Social implications Aligning board gender diversity with sustainability assurance has the potential to enhance the credibility of sustainability reports and mitigate corporate greenwashing for relevant stakeholders. Originality/value The study uses a direct measurement proxy for assurance procedures that ensure the capturing of the nature and extent of assurance procedures used.