The Impact Assessment is an important part of the policy-making process, as it helps in evaluating the potential effects of proposed policies on various stakeholders and making informed decisions about whether to adopt, modify, or reject a proposed policy. It also helps to communicate the benefits of any public investment to society. For these reasons, its importance has grown over recent years, and the Research Infrastructure (RI) policy domain is no exception. The topic has been recognised in ESFRI’s White Paper (2020), where the countries were invited, with support from ESFRI and Horizon Europe, to incentivise RIs to monitor their societal and economic value and impact. Furthermore, the ESFRI Strategy working groups have organised two conferences on this topic (2018 and 2020). Impact assessment is also beneficial for RIs if used to assess and improve the functioning of an RI. It contributes to the strategic planning of an RI, reflecting on internal resource allocation and leading to constant improvement and focussing of services according to the needs of users and other stakeholders. It creates accountability and transparency and hence gives legitimacy, visibility and value to the existence of an RI. Recently, the Competitiveness Council have asked “ESFRI to look into the approaches by Member States, the Commission, international organisations and RIs to assess scientific, societal and economic impacts of investments in RIs, identify good practices, develop a monitoring framework, test it and elaborate recommendations to national and regional RI stakeholders by the end of 2023”. ESFRI has responded to this request by setting up a drafting group tasked with preparing the report based on information collected from literature, surveys and consultations with the ESFRI member countries and RIs. This report highlights the importance of understanding the differences between performance monitoring, which ESFRI started implementing last year, and impact assessment (IA), ex-ante or ex-post, for research infrastructures (RIs). It provides recommendations to stakeholders, policymakers, funders, governments, RIs, ESFRI, and the EC.