Do some firms pay more corporate taxes than others? If so, which types of firms benefit from a reduced tax burden, and how do they achieve this reduction? Are differences in tax rates due to the design of the tax system, to strategic tax planning or to differential enforcement? These questions matter for tax design and are difficult to answer in an empirically founded and comprehensive manner. We use administrative tax data in many countries to systematically calculate firm-level effective tax rates (ETRs) and study how ETRs vary across the firm size distribution. This note shows the results for Uganda, where the corporate statutory tax rate is 30%. We find that the ETR averages 14% across all firms, increases slightly over the firm-size distribution, and drops at the top for the largest firms.