A 'hazard register' is not required by CDM or the ACoP. So it isn't in the ACoP..... The term 'hazard register' is often used to describe a documents that may initially be developed by the client or CDM-C, developed by the designer, then the Contractor - the is finally compiled into the clients H&S File... Its a way of trying to improve the tracking of hazards (and risks) through a project. If you have come across the terms in contract documents then you need to read the documents. If you have come across the term in somebody's Management system then maybe you need to speak with the author. If you've come across the term in an audit report - then speak with the auditor. It's not a 'standard' expression, so there's no 'standard' definition to guide you... Steve