This paper aimed to explore factors influencing the effectiveness of tax audit in Tanzania, by addressing the main question: What can make tax audit effective in Tanzania? This question is important because Tanzania, like many other developing countries, uses a tax audit programme to ensure that satisfactory revenues are submitted by taxpayers, so as to minimize tax avoidance and tax evasion, as well as ensuring a high degree of compliance (Okello, 2014). Because different types of measurements of tax audit effectiveness have been identified by different studies (Ayalew, 2014; Beron et al., 1988; Drogalas et al., 2015; Hasseldine and Bebbington, 1991; Isa and Pope, 2011; Kastlunger et al., 2009), in this study, we used a broad definition of tax audit effectiveness, which considered both direct and indirect effects, which was consistent with Birskyte (2013), Gemmell and Ratto (2012), as well as James and Alley (2002). These studies advocate broadness in addressing tax audit effectiveness. Birskyte (2013) and Gemmell and Ratto (2012) considered that tax audit has two types of effect: a direct effect and an indirect effect. The direct effect is concerned with additional revenue collected as a result of the tax audit, while the indirect effect refers to a deterrence effect, whereby tax auditing is considered to deter potential tax evaders. These views are consistent with earlier views provided by Wickerson (1994) that taxpayer audit programmes are identified as playing not only a deterrence role, but also a wider compliance-enhancing role. As such, our measurement of tax audit effectiveness included transparent procedures to minimize complaints from taxpayers, improvements relating to voluntary tax compliance, proper documentation of tax audit findings, a decline in tax evasion and well-presented tax audit reports.