The project TAX-OWN comparatively studies multi-level residential property fiscal regimes in European cities and their interplay with property-based accumulation and housing policies. The last 30 years have seen an unprecedented rise in housing prices in European cities, and housing has played an increasing role in social inequalities. However, overall residential property taxation seems to have remained stable or even softened in many European countries, which suggests that the appreciation of the housing stock has not been fully captured by property taxes (on transactions, capital gains, inheritance, recurrent taxes on property, etc.). Governments have also willingly forgone revenue through multiple tax reliefs (for homeowners, buy-to-let investors, energy retrofit, etc.). Starting from this tension between property accumulation and tax redistribution, the central goal of this project is to shed light on taxation as a key yet low-visible dimension of public intervention in housing and property, at national and urban levels. Through qualitative and quantitative research, we will address three interrelated research questions: i) How is residential property taxed and how does this differ between types of owners (individual, corporate, public/non-profit), type of uses (primary residence, long-term rental, short-term rental, etc) and between territories? ii) How do taxes capture property values and incomes in large metropolitan areas? iii) How do fiscal authorities (local and national governments) and taxpayers (property owners, intermediaries) use taxation? We will tackle these questions thanks to a comparative, multi-level and mixed methodology analysing the landscape, the combination and the political and social uses of property taxes in large European cities (Greater Paris, Greater London, Greater Milan, studied in their respective states). The taxation of property is considered here as a fundamental mechanism articulating housing-based accumulation, its capture and redistribution by the state, and housing policies at multiple levels of government. The guiding hypothesis of this research is that property taxes (and their combination) shape differential opportunities for property-based accumulation between owners, and that can vary depending on national housing-welfare systems, fiscal decentralisation, local policy agendas and housing markets. First, we will build a database on residential property taxes in European countries (taxes on asset acquisition, disposal, rental revenues, specific fiscal tools such as tax breaks on energy retrofitting, etc.) and study their evolution through three multi-level case studies (France/Paris, UK/London, Italy/Milan). Second, we will shed light on the geography of fiscal regimes between and within the three metropolitan areas, and analyse how taxation is articulated with housing policies, both politically (objectives, trade-offs) and socio-economically (types of owners and properties, etc.). Finally, to go beyond formal rules, we will study tax intermediaries (notaries, tax advisors, online coaches, etc.) who advise property owners in their concrete practices of fiscal compliance and optimisation. Despite being politically sensitive, taxation has been overlooked by comparative urban and housing/welfare research. The project timely contributes to filling this gap. It sheds light on established differences, often invisible, in property fiscal treatment across European cities and owners. It engages with key stakeholders and policymakers in the housing/fiscal fields to identify unequal fiscal gaps for policy advocacy and policy change and feeds a renewed interest in property ownership as a key factor for the understanding of both the unaffordability crises of large urban areas and social inequalities.