Research Infrastructures (RIs) are indispensable for enabling and developing research in almost all scientific domains and represent an increasingly large share of research investment. As policy makers, funding agencies and RI management are increasingly expected to justify key decisions about implementing new projects or investing in existing ones, there is a demand for credible methodologies for assessing the overall impact of RIs. This report proposes a "Framework for assessing the scientific and socio-economic impact of research infrastructures". It aims to provide funders, decision-makers and RI managers with a generic and versatile tool, based on current community practices, to evaluate the achievement of scientific and socio-economic objectives in a realistic way. The framework can be adapted for different types of RIs and different stages in the RI lifecycle. This tool should facilitate the communication and reporting between different RI stakeholders.