Can Environmental Protection Taxes Drive Enterprises Toward Green Transformation?

China’s environmental protection tax (EPT) has been implemented nationwide since 2018, yet its long-term dynamic effects on corporate green transformation remain insufficiently evaluated. Taking the 2018 pollution discharge fee-to-tax reform as a quasi-natural experiment and using data from Chinese listed firms over 2015–2023, this paper employs a difference-in-differences (DID) model to examine the impact of the EPT on corporate green transformation. The results show that after the implementation of the EPT, the green transformation level of firms in heavily polluting industries significantly increased relative to that of firms in less polluting industries; however, this effect only gradually emerged, starting from 2020. Green investor shareholding positively moderates the policy effect, whereas financing constraints exert an inhibiting effect. Heterogeneity analysis reveals that the promoting effect is stronger for small firms, low-tax firms, and regions levying the lower limit of tax rates, and that green credit exhibits differentiated effects; financing constraints and green investors play moderating roles in the impact of the EPT on corporate green transformation. This study provides empirical evidence and policy implications for improving the differentiated collection mechanism of the EPT and strengthening the coordination of fiscal, tax, and financial policies.