An OH&S Management system (OHSMS) is defined as a formalized system that provides organizations with a framework for managing OH&S risks.  The intended outcomes of the OH&S management system are to prevent work-related injury and ill health to workers and to provide safe and healthy workplaces.
So, you have an OHSMS, and the fundamental question is do we need to formalise the system. Most organizations asking themselves this question say 'yes'. And currently, there are more than 40,000 organizations globally that have a formal OHSMS, which is certified to ISO 45001. This number is growing rapidly and we would expect 250,000 certified organizations within 5 years.