The value relevance of mandatory sustainability reporting assurance

Sustainability reporting assurance (SRA) ensures the credibility of sustainability information disclosed by companies. This practice has continued to evolve, particularly within regulatory frameworks. The SRA is widespread among the largest French and South African companies because of the requirements of GRENELLE II and KING III laws. The increased regulation of SRA and the increased rate of obtaining assurance motivated us to conduct our study. This study examines the impact of mandatory SRA on firm value. We run a fixed-effects ordinary least squares (OLS) panel model to test our hypothesis for the 2007–2018 period on a sample of 88 South African listed companies on the Johannesburg Stock Exchange (JSE) and 83 French listed companies on the SBF120 index. We use Tobin’s Q to measure firm value. Our results show a significant positive association between mandatory SRA and firm value. This finding implies that SRA regulations positively affect investors’ perceptions of firm performance, particularly firm value, for two reasons. First, mandatory SRA may strengthen firm legitimacy and establish a good reputation. Second, the adoption of SRA regulations plays an important role in reducing asymmetric information between various actors and solving agency problems between managers and shareholders. Regulators may be interested in the findings when considering current and future assurance requirements for sustainability reporting, and shareholders when considering SRA as an investment choice criterion.