The use of external, independent reviews of CSR(corporate social responsibility) or sustainability management processes and final disclosures is intended to increase the robustness, accuracy and trustworthiness of disclosed information. This study provides an overview of the CSR reports assurance and identifies key potential determinants of the demand for assurance, the choice of assurance provider, level of assurance, and the type of assurance. This study also examines the potential moderating effect of company-level corporate governance characteristics on the assurance decisions. Our sample is obtained from three data sources. Data on carbon emissions are obtained from the Carbon Disclosure Project(CDP), which is released by the Ministry of Environment, and the firm’s CSR or environmental report. The company’s financial statement data are obtained from KIS-Value Databank System. Our final sample consists of 50 firms(126 firm-year observations) in the regression for testing assurance decisions and determinants of the decisions. The main results are summarized as follows: First, the study reveal that firms in ESI (environmental sensitive industry) and regulated industries are not more likely(than firms in other industries) to obtain CSR assurance despite facing significant social and environmental risks. Also, choice of assurance provider and type of assurance are not associated with particular industries. Second, we find that firms with a high eco-efficiency and environmental investment have a negative incentive to voluntarily purchase an independent CSR assurance. However there is no associations between CSR related characteristics(such as eco-efficiency, environmental investment, social contribution expenditure) and the choice of assurance provider. Firms with a high level of social contribution expenditure and environmental investment have a preference for Type2 assurance. The study find several firm characteristics are associated with CSR assurance demand. Third, the results show that large firms and low leveraged firms are more likely to obtain CSR assurance and to choose the accounting profession for an assurance provider. However these firm characteristics are not associated with assurance types. In addition, the results of empirical analysis supported the model that presumed company-level corporate governance characteristics(foreign investor ownership) as moderator. According to the findings of the study foreign investor ownership largely play a role of crucial moderator that intervene in the way which CSR related characteristics(eco-efficiency, social contribution expenditure) affect assurance decisions. In sum, the results of our investigation may help to explain why CSR report assurance remains so limited in this region and what might be necessary to increase its use. Also, our study provides extra insights on CSR or sustainability assurance practice and an understanding of the factors that are correlated with CSR assurance which should be useful for law makers who consider developing policy initiatives for CSR assurance and for accountants or consultants who provide services in such a fast-growing and highly promising market.