The Construction (Design and Management) Regulations 2015 are the UK regulations governing how construction projects are organised for health and safety, from concept to completion.
They define duty holders (client, principal designer, principal contractor, designers, contractors and workers) and require appropriate management arrangements, a construction phase plan, and for notifiable projects an F10 notification. At handover, the health and safety file collects the information future owners and maintainers need.
CDM compliance is evidenced by documents and records: plans, inductions, briefings, inspections. As with most construction obligations, doing it and being able to show you did it are two different disciplines.