This Shared service model has been developed as part of the Connect 4 project funded by the Economic and Social Research Council (ES/Z502972/1) with, as partners, the Office for National Statistics (ONS), Research Data Scotland (RDS), Public Health Scotland (PHS), National Records of Scotland (NRS) and led by EPCC of the University of Edinburgh (EPCC). The Shared service model follows the Connect 4: Roadmap to a federated data service; a document that outlined the changes required to enable a researcher to discover, apply for and analyse data federated across the UK’s national Trusted Research Environments (TREs). For the Roadmap, comparisons were made of two services: the Integrated Data Service (IDS) delivered by ONS and the Scottish National Safe Haven (SNSH) of PHS. Developing technical solutions were out of scope for this remit of work, instead we have taken the analysis and learning from the Roadmap and propose incrementally phased work to take the national TREs towards our vision: A shared, interoperable, research data service that can connect and/or aggregate data from the four UK nations, starting with the Scottish National Safe Haven (SNSH) and Office for National Statistics (ONS) TREs.