CDM 2015 defines a client as anyone for whom a construction project is carried out. 

This definition includes both commercial clients and domestic clients (i.e. clients for whom a construction project is carried out which is not done in connection with a business). 

A client must make suitable arrangements for managing a project, including the allocation of sufficient time and other resources. 

Arrangements are suitable if they ensure that the construction work can be carried out, so far as is reasonably practicable, without risks to the health or safety of any person affected by the project and the facilities required are provided in respect of any person carrying out construction work. 

A client must ensure that these arrangements are maintained and reviewed throughout the project. 

A client must provide Pre-Construction Information (PCI) as soon as is practicable to every designer and contractor appointed, or being considered for appointment, to the project. 

A client must ensure that before the construction phase begins, a Construction Phase Plan (CPP) is drawn up and the Principal Designer prepares a Health and Safety File for the project. 

A client must take reasonable steps to ensure that the Principal Designer complies with any other principal designer duties and the Principal Contractor complies with any other principal contractor duties.

If a client disposes of their interest in the structure, the client complies with their duties by providing the health and safety file to the person who acquires their interest in the structure and ensuring that that person is aware of the nature and purpose of the file. 

Where there is more than one contractor, or if it is reasonably foreseeable that more than one contractor will be working on a project at any time, the client must appoint in writing, a designer with control over the pre-construction phase as principal designer and a contractor as principal contractor. 

The appointments must be made as soon as is practicable, and in any event, before the construction phase begins. 

If the client fails to appoint a principal designer, the client must fulfil the duties of the Principal Designer. 

If the client fails to appoint a principal contractor, the client must fulfil the duties of the Principal Contractor.