Characteristics of the samples.

The implementation of the Environmental Protection Tax Law was a significant milestone in China’s environmental tax reform. The implementation of this law was influenced throughout the three-year period of epidemic prevention and control (from early 2020 to the end of 2022). Heavily polluting enterprises are the primary focus of regulations under the Environmental Protection Tax Law. This study conducts an empirical analysis using a structural equation model, leveraging sample data obtained from heavily polluting enterprises in China. The findings indicate that during the three-year period of epidemic prevention and control, the Porter Hypothesis effect was realized in terms of tax fairness but not in terms of tax rationality. Therefore, environmental tax law reforms should be pursued and tax authorities in China should make vigorous efforts to enhance the rationality of environmental taxation. This would improve the comprehensiveness of the “Porter Hypothesis” effect, fully harnessing the dual functions of environmental protection and the economic driving force embodied by the Environmental Protection Tax Law.