The Health and Safety Executive and the Department for Levelling Up, Housing and Communities have published guidance on:
Building Completion Certificates
How to apply for a completion or partial completion certificate after contractors have completed the building work for higher-risk building work or building work to an existing Higher-Risk Building.
Information can be found here.
Change Control and Notifiable Changes
How to make a change control application for higher-risk building work or building work to an existing higher-risk building.
Information can be found here.