The study findings show that despite sustained annual growth in domestic revenue collections, overall revenue mobilisation in Uganda is still below its potential. Uganda continues to lag behind her regional neighbours in terms of the tax to GDP ratio. Regarding revenue collection efficiency, the tax gap analysis shows that tax collection efficiency (C-Efficiency)—which measures the extent to which tax actual revenues deviate from the maximum possible revenues in a perfectly enforced tax system—is below its potential for all tax categories. In 2015/16, the C-Efficiency ratio was 20.7 percent, indicating that Uganda was unable to collect most of the potential taxes. Nonetheless, the C-Efficiency has significantly increased in the recent past—increasing by approximately 8 percentage points from the average of 11.8 percent, estimated for the period 1991/92 to 2000/01, to an average of 19.7 percent during 2011/12-2015/16.