Understanding Amendment 4
What the Latest 18th Edition Update Means for Electrical Professionals
The Institution of Engineering and Technology (IET), in partnership with the British Standards Institution (BSI), has formally approved Amendment 4 (2026) to BS 7671:2018 – the latest update to the 18th Edition IET Wiring Regulations.
The updated standard – BS 7671:2018 + A4:2026 – will be published on 15 April 2026 and introduces several important technical developments reflecting the evolution of modern electrical systems.
Implementation & Transition of Amendment 4
- Publication: 15 April 2026
- Immediate use permitted: From publication date
- Previous consolidated version withdrawn: Mid-October 2026
From October 2026, Amendment 4 will become the recognised UK standard for:
- New low-voltage electrical installations
- Additions and alterations to existing installations
- Inspection, testing and certification
What’s Changing Under Amendment 4?
Amendment 4 introduces updates that reflect the rapid development of electrical technology, particularly in energy systems and digital infrastructure.
Energy Storage Systems
A dedicated chapter now sets out requirements for stationary secondary battery systems. As energy storage becomes more common in both commercial and residential environments, this provides clearer guidance for design, installation and integration into existing systems.
ICT & Functional Earthing
There is new clarity around functional earthing and equipotential bonding for ICT systems. The regulations now distinguish more clearly between protective earthing and functional earthing, recognising the increasing importance of data-driven infrastructure and structured cabling systems.
Power over Ethernet (PoE)
Specific requirements are now included for Power over Ethernet (PoE) installations. With PoE being widely adopted across lighting, security, access control and network systems, the amendment introduces clearer guidance for safe low-voltage power delivery via data cabling.
Medical Locations (Section 710)
Section 710 has undergone significant revision, strengthening requirements for electrical installations in medical environments. This includes additional criteria and improved recording procedures for supplementary protective equipotential bonding conductors, enhancing patient safety and system resilience.
Why Amendment 4 Matters
This update represents one of the most substantial regulatory developments in recent years. It reflects:
- The growth of renewable and energy storage technologies
- The integration of ICT within electrical infrastructure
- Increasing reliance on low-voltage power distribution systems
- Continued focus on safety, documentation and compliance
Electrical professionals involved in design, installation, inspection and certification will need to ensure their knowledge and practices align with these changes well ahead of the October 2026 transition deadline.
To remain compliant and competitive, professionals should:
- Review the updated BS 7671:2018 + A4:2026 documentation
- Update internal procedures and certification templates
- Undertake CPD or refresher training focused on Amendment 4
- Brief teams and clients on the new requirements
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