A formal written and documented procedure that authorizes certain people to carry out specific work within a specified time frame. It is used to control certain types of work that are potentially hazardous and forms an essential part of safe systems of work for many maintenance activities and allows work to begin only after safe procedures have been defined. It provides a clear record that all foreseeable hazards have been considered. Where the proposed work is assessed as having a high risk, strict controls are required detailing the work and how it will be done. It may require a declaration from those involved in a shift handover of the procedures or extensions to the work that is required to be done. Before process equipment or machinery is returned to service, it may also require a declaration from the permit originator that it is ready for normal operational use.