Digitalisation in international business value chains has exacerbated the misattribution of taxable profits and base erosion into low-tax jurisdictions. Recent responsive proposals discriminate across types of digital or traditional activities and misrepresent synergy within the global business group, thereby worsening misattribution. International business tax literature across economics, law, and policy disciplines neither converge on source-based profit allocation standards nor do they provide a baseline to assess the misattribution of multinational taxable profits.

How, then, should host tax jurisdictions share the global business profits tax base? This thesis proposes that taxable profits of a global business group should be allocated in neutral proportions across all types of business activity, level of digitalisation, and location. This is newly termed as inter-input neutrality. The Cost-based Value Chain Analysis (CVCA) is developed as a practical proposal to realise inter-input neutrality by measuring business activities using costs and deriving a unique group-wide mark-up of taxable profit per activity. This proposal is based on an interdisciplinary theoretical framework utilising tax theory, microeconomic, financial and management accounting concepts. From inter-input neutrality the thesis derives a new baseline to diagnose misattribution - coined as inter-input equity. This baseline requires that activities of the same type, at the least, receive similar allocations of taxable profits, across the multinational business group taxpayer in respective host tax jurisdictions.

Inter-input neutrality establishes a midpoint for jurisdictional shares of the global profits tax base between ad hoc origin-based increments and cumulative differential allocations, as two divergent pathways for long-term reform. CVCA neutrality delivers relational and substantive equality of jurisdictional tax base shares and minimises tax base valuation distortions to business decisions. Finally, the thesis develops an interdisciplinary evaluation framework which integrates tax base shares fairness, efficiency, and administrability criteria to compare the CVCA against the market-based and formulary apportionment proposals.