Comprehensively promoting the digital transformation of enterprises is not just an important prerequisite for achieving high-quality development of enterprises, it is a key driver of building a digital China. This paper takes A-share companies listed on the Shanghai and Shenzhen stock exchanges from 2015 to 2021 as the research object, empirically analyzes the impact and mechanism of the tax credit rating system on the digital transformation of enterprises, and examines the moderating role of the external environment in which enterprises are located. The research results show that the tax credit rating system can significantly promote the digital transformation of enterprises. The mechanism analysis indicates that the tax credit rating system can promote the digital transformation of enterprises through incentive mechanisms and governance mechanisms. The incentive mechanism includes alleviating the financing constraints of enterprises and improving the reputation of enterprises, while the governance mechanism includes enhancing the internal control level and information transparency of enterprises. The heterogeneity analysis reveals that when the external environment uncertainty is low, the social trust level is high, the economic development level is high, and the technological market environment is good, the promoting effect of the tax credit rating system on the digital transformation of enterprises is more significant. In the future, government departments should continuously innovate the management model for micro enterprises and encourage the digital transformation of enterprises through a robust and effective policy package. Enterprises should pay taxes in good faith, regard tax credit as the credit asset of the enterprise, and give full play to its driving role in digital transformation.