The study examines board characteristics, corporate social responsibility (CSR) assurance and social performance disclosure of listed firms before and after mandatory CSR reporting in India. We used the Indian stock market as the testing grounds and applied panel regression and difference‐in‐differences to analyse 960 firm‐year observations between 2010 and 2021. The first findings show that independent board directors and total board size are insignificant in CSR assurance engagement in a mandatory CSR policy period. However, CEO duality is less than likely causing CSR assurance engagement. The second findings show that CSR assurance engagement more than likely causes an increase in social performance disclosure before mandatory CSR policy implementation and increases social performance after policy implementation. The third findings show that the interactive effect of board characteristics (independent directors, total board size and CEO duality) and CSR assurance engagement causes an increase in social performance disclosure. The study sought clarity on the impact of CSR assurance and mandatory CSR reporting on information asymmetry problems to stakeholders. The study also contributes new knowledge on the influence of the interactive effect of board characteristics and CSR assurance on the social performance disclosure of listed firms in India.