Estimating Optimal Corporate Tax Rates under Partial Tax Harmonization: International Empirical Evidence

The introduction of a 15% global minimum corporate tax rate does not seem to be relevant, since it is much discussed in the literature as to its applicability. This paper develops a robust econometric framework to estimate the optimal partially harmonized corporate tax rate across countries. Using a random coefficient and interaction models, we account for structural differences in fiscal responses. The delta method is applied to validate the existence and statistical significance of the harmonized rate. Empirical results show that the optimal partially harmonized rate exceeds the current 15% minimum, with the degree of harmonization varying according to countries’ structural similarity. The study provides a policy-relevant and statistically validated benchmark for international corporate tax coordination. The paper contributes to debates on global tax governance by offering a robust and policy-relevant metric for guiding corporate tax harmonization.