The importance of assigning value to unregistered land may play a crucial role for efficient land management, including acquisition, taxation, and transfer processes. This valuation could be central to establishing tenure security and recognizing legitimate land rights, impacting local and regional economics, governance strength, and the functionality of land markets. The New Urban Agenda highlights the need for competent valuation of unregistered land, which involves a transparent and accountable process, often hindered limited professional expertise, and overall data scarcity. Significant research and guidelines from various organizations, including FIG, FAO, GLTN, Namati, and RICS, have contributed to the understanding of the valuation of unregistered lands. These efforts have resulted in publications such as the Valuation of Unregistered Lands: A Policy Guide by UN-Habitat, providing practice-based guidance for valuation related to land-based financing, taxation, and fair compensation assessments. This guide together with the manual developed is universally applicable, offering a comprehensive framework for valuing unregistered land in various contexts and locations. It incorporates established best practices and protocols, detailing key valuation concepts, professional capacity-building, and includes practical tools for valuation professionals. As part of the ongoing revision of the ISO 19152 the Land Administration Domain Model (LADM), which includes a Part 4 focused on valuation, questions arise concerning the adaptability of the Social Tenure Domain Model (STDM) to address the valuation of unregistered land. This paper investigates whether STDM can be extended to accommodate the specific demands of the valuation of unregistered land and explores the necessary modifications required to develop such an extension that is both sophisticated and practically applicable in an informal setting. To effectively extend STDM for valuation purposes, it is crucial to incorporate specific valuation functions capable of capturing land values based on various criteria like location, land use, and potential for development. These functions must be adaptable to different economic conditions and real estate markets to ensure accuracy and relevance also in an informal setting. The model must also enhance its data integration capabilities to manage a range of data sources effectively, including market data, but also not formally recognised supporting documents. Considering the contexts in which STDM is typically used, the model should feature user-friendliness and not too complicated procedures that are intuitive and accessible for individuals without formal training. Simplifying both the input and output processes is crucial to ensure the model's usability and clarity. Furthermore, the model should be scalable to handle various sizes and types of buildings and plots and flexible enough to adapt to diverse local legal and economic environments. Further, and this is crucial to any standard development, interoperability must be ensured so that the data can also be included in any formal system used within the specific country. This paper describes the development of the STDM Valuation of Unregistered Land and how specific aspects and considerations were derived from literature and practical experiences to develop such an extension. With the development of the STDM Valuation of Unregistered Land the aim is to contribute to more equitable and effective land administration practices worldwide.@en