Tax registration drives have become an increasingly popular intervention to expand the coverage of tax nets across sub-Saharan Africa. However, doubts have recently been casted on their impact, as there is increasing evidence that they do not lead to a substantial increase in revenue, and might skew the tax registry so that towards vulnerable groups are overrepresented. There is little explanation available for these outcomes, as the literature focuses on the outcomes of these exercises – rather than on their processes and premises. We seek to fill this gap through an evaluation of a tax registration exercise of small- and medium-sized enterprises in Freetown, Sierra Leone, implemented by the National Revenue Authority. We argue that the conflicting objectives between national and international stakeholders, as well as between street- and higher-level officials, combined with a technocratic view of the exercise that underestimated its political nature, led to its likely unsatisfactory outcome in revenue terms. However, we also identify non-revenue outcomes that may still be seen as positive from the perspective of policymakers, such as familiarising many businesses with a revenue authority that they previously had very little engagement with. While this outcome of registration exercises is frequently overlooked by similar evaluations, it is one that local officials recognise as important in ‘building future taxpayers’.