Intergovernmental Fiscal Relations, Tax Jurisdiction Conflicts, and Subnational Revenue Optimisation in Nigeria

This doctoral study develops a comprehensive theoretical and empirical analysis of intergovernmental tax jurisdiction conflicts in Nigeria and their implications for subnational revenue optimisation. Nigeria's constitutional tax assignment, divided across the exclusive, concurrent, and residual legislative lists, has generated persistent disputes between the federal government, states, and local governments over the right to levy, administer, and retain revenues from key tax bases including VAT, personal income tax on pensions, and mineral royalties. These conflicts create investment uncertainty, administrative duplication, and revenue leakage. The study combines a legal-constitutional analysis of tax jurisdiction disputes adjudicated by the Supreme Court since 2000 with an econometric assessment of how jurisdictional ambiguity affects subnational revenue performance. A game-theoretic model of intergovernmental tax competition is developed, extending the Zodrow-Mieszkowski framework to incorporate the Nigerian federalism's three-tier structure and the distorting role of oil transfers on state tax effort. The model derives Nash equilibrium tax effort conditions under different assignment clarity regimes. Empirical testing uses a state-level panel dataset with a jurisdictional conflict intensity index constructed from court case records and legislative dispute data. The study expects to find that higher jurisdictional conflict intensity significantly reduces state tax effort and IGR efficiency. Theoretical contributions include the three-tier intergovernmental tax competition model adapted to oil-dependent fiscal federalism. Keywords: intergovernmental fiscal relations, tax jurisdiction, subnational revenue, fiscal federalism, game theory.