This dataset provides panel data for 168 firm-year observations from companies included in the SRI-KEHATI Index between 2018 and 2024. The dataset was developed to examine the role of CEO characteristics and environmental costs in influencing sustainability disclosure and corporate tax avoidance practices. The variables include CEO educational background, CEO age, CEO tenure, CEO nationality, CEO gender, environmental cost, sustainability disclosure score, tax avoidance measures, and several firm-level control variables. Data were manually collected and verified from annual reports, sustainability reports, and audited financial statements published by the sampled firms. The dataset supports the analysis of potential decoupling behavior, where firms may exhibit extensive sustainability disclosures while simultaneously engaging in tax avoidance activities. It is intended to facilitate replication, validation, and extension of research in sustainability accounting, corporate governance, environmental management, and taxation.