The aim of the report is to support data infrastuctures on their journey towards certification and the provision of trustworthy repository services that enable FAIR data. As well as describing the co-dependencies between (meta) data objects and their repository environment, and mapping requirements to principles, the report explains the evolving capability/maturity approach and lays out the design of a governed assessment and certification process. This work will iterate alongside a variety of ongoing data infrastructure initiatives to support a range of stakeholders on their journey towards the provision of trustworthy repository services that enable FAIR data.