Modern research is impossible without software. From short, thrown-together temporary scripts to solve a specific problem, through an abundance of complex spreadsheets analysing collected data, to the hundreds of software engineers and millions of lines of code behind international efforts such as the Large Hadron Collider and the Square Kilometre Array, there are few areas of research where software does not have a fundamental role. Further, this is not just research based on the "traditional" users of computational infrastructure. Data science and "big data" would not be possible without software to access, analyse, visualise, send and store that data. Software use is also not restricted to the physical sciences: the use of research software is even across all disciplines, with 68% of researchers reporting that their research would be impossible without research software. The capacity of all researchers, in the UK and worldwide, to generate new insights depends on the availability of research software and the ability of researchers to use it (better software, better research). During the next phase of the Institute, we will focus on the domains of each of the Research Councils (particularly BBSRC, EPSRC and ESRC) and help their researchers gain the most from available services to improve the sustainability, engineering, reuse, quality and recognition of software. To deliver this, the Institute's work is split into five themes: Community: bringing people together via events and networks to identify, understand and facilitate solutions for common challenges; Policy: research into the social, economic and technical drivers of the research software community, understanding its needs, and then working to enact the required changes through campaigns; Research Software: working directly with researchers who are developing software to ensure it meets the needs of reliable, reproducible and reusable research; Training: coordinating, defining, and delivering training on software development and data science skills to UK research organisations, and working to build a sustained training platform; Communications: ensuring the work of the Institute is disseminated to the widest possible audience, and working with collaborators to amplify the impact of our work. With the help of additional studies extending the work above, we will conduct research-council specific campaigns tailored to the needs of the researchers to help increase the uptake of services (not just those offered by the Institute, but those funded by the research councils) that are already available and define services which are lacking. This will not only help researchers from all research domains acquire the skills they need for modern research (helping researchers help themselves), but will also ensure that the lessons learned within one domain are transferred to the others - keeping the UK at the forefront of world-leading research.

Software is fundamental to research, fulfilling many different roles - instrument, model, tool, infrastructure - across all disciplines. Recent shifts in the wider research landscape, e.g. inclusion of research software in policies developed by the OECD and UNESCO, necessitate new approaches to software sustainability and consolidation and scaling of existing initiatives to support research software (the software used in research) and digital research infrastructure (the compute, data, networking, software and people infrastructure) that enables it. Thus far, support for research software has tended to focus on individuals or national policies and standards. Moving forward, organisations such as universities and other research institutions will play an increasingly important role in ensuring research software culture and practice is adopted by the research community. This is essential to empower those engaged in research to fully harness the potential of software and foster the execution of excellent research. The Software Sustainability Institute (SSI) was established in 2010 as the first organisation in the world dedicated to the development and support of research software best practices. In its first phase (2010 - 2015), the SSI gained an understanding of the state of the nation of research software, its developers/users, its requirements, and the importance of software for conducting research. The second phase (2015 - 2019) focussed on supporting communities to become self-sustaining and campaigning for change in research culture. In the third phase (2018 - 2024), the SSI consolidated its position as world-leading experts in research software policy and best practices. The SSI also scaled up its highly successful activities to make them more sustainable in the longer term. Throughout, the SSI has fostered a large, collaborative, worldwide community of advocates and practitioners to help deliver on their motto: better software, better research. The fourth phase of the SSI will continue enhancing and scaling its signature activities, including the fellowship programme, community building, career development and training. It will continue to campaign for the recognition of all of the people and outputs that contribute to research and add a new focus on environmental sustainability and empowering organisations to take responsibility for the research software they create and use. Four impacts will guide the work in SSI-4: 1. Evidence-driven research software policy and guidance. 2. Capable research communities. 3. Widespread adoption of research software best practice. 4. Broadened access and contributions to the research software community. The SSI will achieve these through: - Building on its successful platforms and campaigns: empowering individuals through the Fellowship Programme, amplifying dissemination through online resources and social media, raising awareness of research software through events, and campaigning for policy and research culture change. - Growing its policy and research activities: building on SSI national landscape studies, collaborating on the HiddenREF campaign, creating new connections to further embed software into UK research policy. - Developing new training courses, learning pathways, communities of practice handbooks, and bringing the community together through the Collaborations Workshop. - Co-producing research to explore the barriers and enablers to career progress, commissioning articles and guides from a diverse range of authors, and running workshops in other, non-English, languages. - Coordinating an innovative software funding pilot to better understand how research software maintenance and development should be funded.