Urban Decay, Negative Territorial Externalities and the IPTU Tax Base: A Legal-Tax Analysis of Violence and Institutional Abandonment as Causes of Real Estate Devaluation

This article analyzes, from the perspective of Constitutional Tax Law and Urban Law, the relationship between negative territorial externalities and the tax base of the Urban Property Tax (IPTU) in Brazil. It argues that urban decay—driven by persistent urban violence and the abandonment of large private institutional anchors—produces measurable real estate devaluation, distorting the economic basis of property taxation. The study identifies a structural asymmetry in the Brazilian tax system: while legal mechanisms such as the betterment contribution allow the State to capture increases in property value resulting from public works, there is no equivalent instrument to address value depreciation caused by collective negative externalities. As a case study, the article examines the closure and abandonment of the Universidade Gama Filho in Rio de Janeiro, demonstrating how institutional omission and the lack of timely urban policy intervention contributed to territorial degradation and economic decline in the surrounding area. The research adopts an interdisciplinary approach by incorporating insights from criminology, particularly the Broken Windows Theory, to explain the causal link between urban disorder, criminality, and property devaluation. Finally, the article proposes the creation of legal mechanisms to adjust the IPTU tax base in areas affected by proven urban degradation, grounded in constitutional principles such as ability to pay, tax fairness, and prohibition of confiscatory taxation, while also drawing on comparative experiences such as Tax Increment Financing (TIF). Este artigo analisa, sob a perspectiva do Direito Constitucional Tributário e do Direito Urbanístico, a relação entre externalidades territoriais negativas e a base de cálculo do IPTU no Brasil, demonstrando como fatores como a violência urbana e o abandono institucional podem gerar distorções relevantes na tributação imobiliária.