The research aims to examine the mediating effect of sustainability disclosure on the relationship between proactive tax planning and firm value among companies listed in the ESG100 Index. The sample comprises 114 firm-year observations from ESG100 companies during the period 2020 to 2022. This study utilizes secondary data. Moreover, a statistical regression method was applied using balanced panel data analysis, integrating both cross-sectional and time-series data to test the research hypotheses. The findings indicate that proactive tax planning has no significant effect on sustainability disclosure. However, sustainability disclosure has a positive and significant effect on firm value, whereas proactive tax planning has a negative and significant effect on firm value. This suggests that proactive tax planning may reduce firm value due to associated costs, such as tax advisory fees. Executives should therefore carefully evaluate the costs and benefits of proactive tax planning and choose strategies that optimize long-term benefits for the company. Understanding the tax costs involved in business operations should be a priority for management. The study's findings also suggest that regulatory authorities should develop tax policies that are contextually appropriate for Thailand and align with current economic conditions. In addition, the study reveals that investors place a high value on sustainability disclosure.
Adthajak et al. (Wed,) studied this question.