The aim of this paper was to substantiate tax audit and investigation as imperatives for the achievement of an efficient tax administration in Nigeria. The study adopted an expository approach using content analysis of existing literatures. The doubt and sociological theories were used to firm up the conceptualization of the topic. The study revealed that tax audit and investigation are inevitable to improve on the collection of tax revenues in Nigeria. The study also confirmed that there is a high prevalence of non-compliance currently among individuals and companies in the country. The paper, therefore, called on the government to provide an enabling legislation to make non-compliance with tax laws a more serious offence with stiffer penalties. This paper has added fresh authoritative literature to the field of taxation in Nigeria and would prove useful to other tax researchers, the relevant tax authority administrators and other policy makers in Nigeria.