Global Minimum Tax, Pillar Two Implementation, and Fiscal Sovereignty Implications for Nigeria

This doctoral study conducts a comprehensive theoretical and policy analysis of the OECD/G20 Global Anti-Base Erosion framework, known as Pillar Two, and its implications for Nigeria's fiscal sovereignty, corporate tax revenue, and investment incentive architecture. The global minimum tax, establishing a 15 percent effective minimum tax rate for multinational enterprises in scope, represents the most significant multilateral tax reform in decades. For Nigeria, which deploys a range of sub-minimum tax incentive structures to attract investment, Pillar Two creates both compliance obligations and strategic repositioning requirements for fiscal policy. The study first develops a comprehensive mapping of Nigeria's existing corporate tax incentive landscape, identifying incentives that reduce effective tax rates below the 15 percent threshold and thereby become subject to top-up tax collection under the income inclusion rule or the undertaxed profits rule. Using confidential FIRS large taxpayer data on effective tax rates, the study estimates the revenue implications of Pillar Two for Nigeria under three implementation scenarios: immediate full adoption, partial adoption with qualified domestic minimum tax, and non-adoption. A fiscal sovereignty analysis, drawing on international law and political economy frameworks, examines the implications of Pillar Two participation for Nigeria's legislative and treaty-making autonomy. The study expects to find that a qualified domestic minimum top-up tax is the welfare-superior strategy, allowing Nigeria to capture top-up revenue currently collected by residence-state jurisdictions while retaining policy design flexibility. Keywords: global minimum tax, Pillar Two, BEPS, fiscal sovereignty, Nigeria.