What must dutyholders do? The designer

Where it is not possible to eliminate health and safety risks when preparing or
modifying designs, designers must ensure appropriate information is included in the
health and safety file about the reasonably practicable steps they have taken to
reduce or control those risks. This will involve liaising with:
(a) the principal designer, in helping them carry out their duty to prepare, update,
review and revise the health and safety file. This should continue for as long as
the principal designer’s appointment on the project lasts; or
(b) the principal contractor, where design work is carried out after the principal
designer’s appointment has finished and where changes need to be made to
the health and safety file. In these circumstances, it will be the principal
contractor’s duty to make those changes, but the designer must ensure that
the principal contractor has the appropriate information to update the file.
This information should be provided to the principal designer and principal
contractor as early as possible before the designer’s work ends on the project.