Amendment 4 (BS 7671:2018+A4:2026) was published on 15 April 2026. It is the most significant update to the 18th Edition since Amendment 2 in 2022, and it also rolls Amendment 3:2024 into a single consolidated book. For the first time, the Wiring Regulations include dedicated requirements for battery storage and for the data-and-power systems that have quietly become part of nearly every modern building.
The short version: the old edition (BS 7671:2018+A2:2022+A3:2024) and Amendment 4 run side by side during a six-month transition. From 15 October 2026 the previous edition is withdrawn, and new installation work should be designed and certified to Amendment 4. There is no need to re-certify existing installations simply because the standard has changed.
The five changes that matter
Battery storage gets its own chapter
Chapter 57A brand-new chapter covers stationary secondary batteries – the fixed battery systems that pair with solar PV, provide back-up, or export to the grid. It deals with selection, installation, protective earthing, shock and thermal protection, and the notices and identification a battery installation needs.
For installations in dwellings, Chapter 57 requires you to follow PAS 63100:2024, the specification for protecting against fire from domestic battery energy storage. PAS 63100 is best-practice guidance (not statute), and it advises against locations such as lofts, roof spaces and escape routes.
Who it affects: solar & storage installers, EV installers branching into battery.
Functional earthing for ICT
Section 545A new section addresses functional earthing and functional equipotential bonding for information and communication technology – broadcast, communications and computer networks. It draws a clear line between functional earthing (for correct operation and EMC) and protective earthing (for safety), and covers conductor sizes, identification, continuity and the main functional earthing terminal.
Who it affects: anyone wiring structured cabling, comms rooms or smart-building infrastructure.
Power over Ethernet
Section 716A new section for the use of balanced data cables to carry extra-low-voltage DC power as well as data. As PoE-powered cameras, access points, door entry and LED lighting have spread, this section sets out how to design, install and verify cabling that does both jobs at once.
Who it affects: installers of CCTV, access control, networking and PoE lighting.
Medical locations, substantially revised
Section 710Section 710 receives its biggest revision since the 18th Edition. Power supply arrangements for Group 2 medical locations are redrafted to prevent a single fault cutting power to life-supporting equipment, requirements for medical insulation monitoring devices are extended, and supplementary equipotential bonding is expanded. A new model form (Annex B710) is introduced for recording the resistance of supplementary protective bonding conductors.
Who it affects: contractors working in hospitals, clinics, dental and veterinary premises.
Energy efficiency moves up
Part 8 / Chapter 81The energy-efficiency material that previously sat in the informative Appendix 17 has been reworked into a new Part 8, headed by Chapter 81. It provides a framework for designing installations with energy efficiency in mind, pointing across to the relevant Building Regulations for each UK nation.
Who it affects: anyone designing or specifying larger installations.
What changed on the certificates
Amendment 4 also updates the model forms in Appendix 6. Two changes are worth knowing before you issue your next certificate:
Two signatures. The Electrical Installation Certificate, Condition Report and Minor Works Certificate now separate the person who carried out the inspection and testing from the person authorising the report for issue – each signs their own block.
Photographs are in. The Condition Report now explicitly allows photographic and thermographic images to be attached as supporting evidence for observations.
So what do you actually need to do?
If you certify electrical work, you will need to be working to Amendment 4 for new installations designed from 15 October 2026. In practice that means getting familiar with the new chapters now, while the transition period gives you breathing room, rather than the week the deadline lands.
And to be clear: this guide does not replace the book. It is a plain-English orientation to help you see what has changed and where. The published standard, BS 7671:2018+A4:2026, remains the authoritative reference you must design to, certify against, and quote to Building Control. You will also need it for scheme registration and qualifications. Think of this page as the map, not the territory.
This guide is an original, plain-English summary written by Creative Machines. It does not reproduce any BS 7671 text, tables or diagrams, which remain the copyright of the IET and BSI. Section and chapter numbers are cited as factual references. Always verify the specific requirements for your installation against your own copy of BS 7671:2018+A4:2026 and consult your local Building Control Body where required.