The IET Wiring Regulations is the national standard for electrical installations in domestic, commercial and industrial settings. It is the essential standard for all those concerned with the design, installation, certification and maintenance of electrical installations. Amendment 4:2026 is a major update to BS 7671:2018, The IET Wiring Regulations, Eighteenth Edition. BS 7671:2018+A4:2026 is a consolidated publication which incorporates all previous amendments to the standard. New inclusions within BS 7671:2018+A4:2026 are: Stationary Secondary Batteries where the purpose is for electrical storage and supply of electrical installations; Functional earthing and functional equipotential bonding for information and communication technology (ICT) equipment and systems; a new section on Power over Ethernet (PoE) and a major revision of Section 710 Medical Locations and the inclusion of a schedule of test results for recording the resistance of supplementary protective equipotential bonding conductors. From 15th April 2026 you will need to have a copy of BS 7671:2018+A4:2026, known as 'the orange book'.