This work addresses identifier recommendations and harmonisation in the context of the BMS Research Infrastructures (RIs) participating in CORBEL. We summarise community activities in this space (Appendix 1), provide two checklists for: (i) RI identifier strategy and (ii) identifier harmonisation of common entities and services for identity use cases which span the participating BMS RIs. We use six case studies to guide the work. We also define priorities and document existing services that can be adopted, or extended in support of CORBEL.