This falls into two sections. The H&S you are required to have by law, and the H&S principal contractors insist you have before carrying out work for them. A principal contractor can demand any document they wish, and you either have to supply it if you want to work for them or you loose out to a competitor.
As a legal requirement you will need risk assessments, COSHH assessments and a company H&S policy if you employ more than four people.
As a bare minimum, most CDM sites ask for method statements as well and then you may also be asked for such things as equality and diversity policies, staff training records, lone worker policies and PAT test records.
In this package we include relevant risk assessments, method statements and COSHH assessments but not the company H&S policy.
The reason a Company H&S policy is omitted is because it’s not specifically relevant to a particular task. Instead it’s a stand alone document that covers your general approach to H&S within your company and who is responsible for what.