A COMAH notification is a simple process that applies to lower and upper tier COMAH establishments, and sites that are planning to be outside the COMAH regime. A notification is required in advance of changes that could result in significant consequences at COMAH establishments. In addition, COMAH Regulations 2015 requires a re-notification by all COMAH establishments. For upper tier establishments, the submission of a revised safety report does not preclude the fulfilment of this duty.