This specification is concerned with the safety of patients and gives guidance on the analysis and categorisation of hazards and risks to patients from health informatics products, to allow any product to be assigned to one of five risk classes. It applies to hazards and risks which could cause harm to a patient. Other risks such as financial or organisational are out of scope unless they have the potential to harm a patient.This Technical Specification applies to any health informatics product whether or not it is placed on the market and whether or not it is for sale or free of charge. Examples of the application of the classification scheme are given.