Government revenue mobilisation in Nigeria continues to depend heavily on the willingness and capacity of tax authorities to detect non-compliance and of taxpayers to meet their statutory obligations. Tax audit and tax compliance have long been treated in the literature as separate determinants of revenue outcomes, yet the channel through which audit activity is converted into compliance behaviour, and ultimately into collected revenue, has received far less conceptual attention, particularly since the enactment of the Nigeria Tax Administration Act, 2025 and the establishment of the Nigeria Revenue Service. This paper undertakes a descriptive, desk-based conceptual review of tax audit, tax compliance, and revenue generation in Nigeria, with particular emphasis on the possible mediating role of tax administration efficiency under the new 2025 tax administration architecture. Drawing on conceptual, theoretical, and empirical literature published largely between 2020 and 2025, the paper argues that tax audit exerts its strongest influence on revenue generation not directly, but through the compliance behaviour it induces, and that the strength of this pathway is itself conditioned on how efficiently the revenue authority administers assessment, audit selection, and enforcement. The paper proposes a conceptual mediation model in which tax administration efficiency, newly reconstituted under the Nigeria Revenue Service, occupies a pivotal position between audit activity, taxpayer compliance, and realised revenue. Theoretical, managerial, and policy implications are drawn, and the paper closes with its contribution to knowledge, its limitations, an agenda for further empirical testing, and a statement on the ethical conduct of the review.