Effective Tax Rates, Firm Size and the Global Minimum Tax

We document new facts on corporate taxation and the revenue potential of corporate minimum taxes, leveraging firm-level tax returns from 16 countries. First, effective tax rates (ETRs) follow a hump-shaped pattern with firm size: small firms benefit from reduced rates, while large firms take up tax incentives, leaving mid-sized firms with the highest ETRs. On average, the ETR for the largest 1% of firms is 2.2 percentage points lower than the average ETR for top decile firms. Second, although statutory tax rates are above 15% in all sample countries, over a quarter of top firms face an ETR below 15%, challenging the simple tax haven vs non-haven dichotomy. Third, a simple 15% domestic minimum tax for the top 1% firms could raise corporate taxes by 14% on average across countries, absent behavioral responses. In contrast, the global minimum top-up tax would only raise a quarter of this revenue due to its generous deductions and a smaller number of firms in scope.