In alignment with the global trend towards mandatory sustainability reporting, the Korean government mandates sustainability reporting for all listed companies by 2030. This regulatory shift requires enhanced responsibility and transparency from firms in disclosing their ESG activities. Hence, this study aims to provide policy insights by analyzing domestic companies" sustainability reports and third-party assurance between 2016 and 2022. Recent findings highlight incomplete ESG reporting: selective Scope3 emissions reporting, omitting legal sanctions, and using discretionary criteria for ESG data disclosure. Employing Python programming, this study comprehensively collects and analyzes sustainability reports of listed companies. Through detailed case analyses, this study proposes policy directions for sustainability reporting obligations.