ISO 45001:2018 4.3: Determining the scope of the OH&S management system
In defining the scope, the organization works out where the system's boundaries lie and what it applies to, taking into account its external and internal issues, the requirements of interested parties, and the work-related activities it plans or carries out. The system covers those activities, products and services that the organization controls or influences and that can affect its OH&S performance, and the scope is available as documented information.
This control maps to 17 controls across 16 other frameworks. If you already hold one of them, the evidence you collected for it is the starting point here rather than new work.