BS 7671 Amendment 4 Transition Period Explained: What Happens Before October 2026?

TL;DR

• BS 7671 Amendment 4 was published in September 2024 and becomes fully mandatory in October 2026.

• During the transition period, electrical work may comply with either the original 18th Edition or the amended version.

• New designs and installations should now be carried out to Amendment 4 standards.

• Key changes include expanded AFDD requirements, updated EV charging rules, revised SPD guidance, and new renewable energy provisions.

• Duty holders should review upcoming EICRs, commission new work to Amendment 4, and confirm their contractors are trained on the updated standard.

If you manage commercial or industrial premises in the UK, BS 7671 should already be on your radar. It is the national standard governing electrical installations, setting out the rules that qualified electricians must follow to keep buildings safe.

In September 2024, the Institution of Engineering and Technology (IET) published Amendment 4 to BS 7671:2018, the 18th Edition Wiring Regulations. The amendment introduces significant technical changes. But before full mandatory compliance applies in October 2026, there is a transition period that has created uncertainty for duty holders, facilities managers, and electrical contractors.

This guide explains what the transition period means, how it affects ongoing and new electrical work, and what you should be doing now to prepare. For a full breakdown of the technical changes, see our detailed BS 7671 Amendment 4 summary.

What Is BS 7671 Amendment 4?

BS 7671 is the UK standard for electrical installations in buildings. Published by the IET and the British Standards Institution (BSI), it sets the minimum safety requirements for how electrical systems must be designed, installed, and verified.

Amendment 4, formally known as BS 7671:2018+A4:2024, is the fourth amendment to the current 18th Edition. It updates specific sections where technical requirements have evolved, new technologies have emerged, or practical experience has identified gaps in the existing rules.

When Was Amendment 4 Published?

Amendment 4 was published in September 2024. From that point, contractors could begin working to the new requirements, but a transitional arrangement was put in place to allow the industry time to adapt before full mandatory compliance was required.

What Does Amendment 4 Change?

The amendment updates several key areas of BS 7671, including:

• Arc fault detection device (AFDD) requirements, extended to a wider range of premises

• Electric vehicle (EV) charging installation rules under the updated Section 722

• Surge protective device (SPD) requirements and application guidance

• Requirements for installations associated with renewable energy sources, including solar PV systems

• Protective measures and documentation requirements for certain high-risk environments

What Is the Transition Period?

The transition period runs from September 2024, when Amendment 4 was published, through to October 2026. During this window, the industry is expected to familiarise itself with the new requirements and migrate to the updated standard.

Installations completed during this period can technically comply with either the pre-amendment 18th Edition or the amended version, depending on when the design work began and which version was in use at that time.

When Does the Transition Period Start and End?

The transition period runs from September 2024 to October 2026. After that point, all new electrical installation work in the UK must comply with Amendment 4. There is no extension anticipated, and the industry has had over two years to prepare.

What Does Dual Compliance Mean?

During the transition period, both the original 18th Edition and the amended version are technically acceptable. This is sometimes called dual compliance. In practice:

• Designs started before September 2024 may continue under the pre-amendment standard

• New designs and installations should now be carried out to Amendment 4

• Contractors and inspectors need to understand both versions to assess and certify work correctly

This can create confusion on site, particularly where refurbishment projects span the transition boundary or where different contractors are involved at different stages of the same project.

What Changes During the Transition Period?

The transition period has practical implications for everyone involved in electrical compliance.

For Electrical Contractors

Contractors need to be familiar with Amendment 4 from now. While dual compliance is technically permitted, clients and duty holders will increasingly expect new work to meet the updated standard. Contractors who are not trained on the new requirements risk issuing incorrect certification or falling behind on compliance expectations.

From a legal standpoint, designing and installing to the most current standard is the safer position. If something goes wrong on an installation that used the pre-amendment rules when the updated version was available, that decision may be scrutinised during a subsequent investigation or insurance claim.

For Duty Holders and Facilities Managers

Duty holders are responsible for ensuring electrical installations in their premises are safe and legally compliant. During the transition period, this means:

• Any new electrical work commissioned should be carried out to Amendment 4

• Ongoing refurbishment projects should be reviewed to confirm which version of the standard applies

• Documentation and certification should clearly state which edition of BS 7671 was used

• Planned inspections should clarify with your contractor which standard the assessment is carried out against

For EICRs Carried Out Before October 2026

An Electrical Installation Condition Report (EICR) assesses the safety of an existing installation against the standard in force at the time of the original installation. During the transition period, an EICR will not automatically fail an installation for lacking AFDDs or other Amendment 4 features. However, inspectors should note where an installation falls short of the latest edition as an observation or recommendation.

Our fixed wire testing services are carried out with full Amendment 4 awareness, helping you identify any gaps and plan upgrading works before the mandatory deadline.

Key Technical Changes You Need to Know

Arc Fault Detection Devices (AFDDs)

One of the most significant practical changes in Amendment 4 is the expanded requirement for AFDDs. These devices detect dangerous arcing faults in wiring that can cause fires even where conventional circuit protection would not trip. Under Amendment 4, AFDDs are required in a wider range of premises, including certain commercial, residential, and educational settings.

For facilities managers, this means future refurbishments and new fit-outs may require AFDDs on final circuits where they were not previously needed. Planning for these devices early avoids costly last-minute changes during construction or handover.

EV Charging Installations (Section 722)

The growth of electric vehicles has prompted significant updates to Section 722, which governs EV charging installations. Amendment 4 introduces revised requirements covering load management and smart charging systems, protection against electric shock and overcurrent, and documentation requirements for EV charging infrastructure.

If your premises include EV charging points or you are planning to install them, the updated Section 722 requirements apply to any new installation from September 2024. Our EV charging point testing services are delivered in line with the latest standard.

Surge Protective Devices (SPDs)

SPDs protect electrical equipment from voltage spikes caused by lightning strikes or switching operations. Amendment 4 includes updated guidance on when SPDs are required and how they should be specified and installed. For commercial buildings with sensitive electronic equipment, medical devices, or data infrastructure, the revised SPD requirements may influence future installation decisions.

Renewable Energy Sources

With the continued growth of solar PV and battery storage in commercial buildings, Amendment 4 updates the requirements for installations associated with renewable energy, including protection and documentation standards for solar PV arrays and associated inverter equipment. If your premises have or are planning rooftop solar or battery backup systems, these updates are directly relevant.

What Should You Do Before October 2026?

With the deadline approaching, here is what responsible duty holders and compliance teams should be doing now:

• Commission all new electrical work to Amendment 4. Any new installation or significant refurbishment should be designed and installed to the updated standard from this point forward.

• Review ongoing projects. If a refurbishment was designed before September 2024, confirm with your contractor which version of BS 7671 applies and whether any elements need updating.

• Check your EICR schedule. If your fixed wire testing is due in 2025 or 2026, use the inspection to understand where your installation may need upgrading before the deadline.

• Confirm your contractor is trained on Amendment 4. A competent contractor should demonstrate familiarity with the changes and certify work to the updated standard.

• Plan for AFDD and EV charging upgrades. Start planning now to avoid rushed decisions as October 2026 approaches.

Protest ES Ltd provides electrical compliance services across commercial and multi-site portfolios, with full Amendment 4 awareness built into every inspection and installation project.

How Does This Affect EICRs and Fixed Wire Testing?

EICRs and fixed wire testing assess the safety of existing electrical installations. During the transition period, inspections are carried out against the standard that applied when the installation was completed, not the latest version of BS 7671.

However, a competent inspector will note where an existing installation does not meet the requirements of Amendment 4, flagging these as recommendations or observations in the report. This gives duty holders a clear picture of any upgrading works needed before October 2026.

If your EICR is due within the next 12 to 18 months, discuss the Amendment 4 transition with your testing contractor in advance. Understanding where your installation stands early gives you more time to budget and plan any electrical remedial repairs that may be required.

Frequently Asked Questions

When does BS 7671 Amendment 4 become mandatory?

Amendment 4 becomes fully mandatory in October 2026. From that point, all new electrical installation work in the UK must comply with the updated standard. During the transition period from September 2024, both the original 18th Edition and the amended version are technically acceptable, but new designs should comply with Amendment 4 from now.

Can electrical contractors still use the 18th Edition during the transition period?

Yes. During the transition period, a contractor can work to either the pre-amendment 18th Edition or Amendment 4, depending on the project circumstances. For any new design started after September 2024, working to Amendment 4 is considered best practice and reduces the risk of compliance disputes after the mandatory deadline.

Will my existing EICR become invalid because of Amendment 4?

No. An EICR assesses an existing installation against the standard applicable when the installation was completed. A valid EICR will not become automatically invalid because of Amendment 4. When your next inspection is due, the inspector may note where the installation does not meet Amendment 4 requirements and flag these as recommendations for upgrading works.

Are AFDDs now required in all commercial buildings?

Amendment 4 expands the requirement for AFDDs, but they are not required in every building or on every circuit. The specific requirements depend on the type of premises, the nature of the installation, and the condition of the existing wiring. Your electrical contractor can advise whether AFDDs are required in your particular circumstances.

Does Amendment 4 affect EV charging installations already in place?

Amendment 4 sets new requirements for EV charging installations, but existing compliant installations will not automatically need to be upgraded. The updated Section 722 requirements apply to new EV charging installations from September 2024. If you are planning new charging points or expanding existing EV infrastructure, your contractor must comply with the updated requirements.

What documentation should contractors provide during the transition period?

Contractors should provide standard certification for the work carried out: an Electrical Installation Certificate (EIC) for new installations, or an EICR for inspection work. The certification should clearly state which edition of BS 7671 was used as the basis for the work. This is important for audit and compliance purposes, particularly where work spans the transition period.

What happens if electrical work is carried out after October 2026 without complying with Amendment 4?

After October 2026, any new electrical installation work that does not comply with Amendment 4 will be non-compliant with the current national standard. This creates legal liability for both the contractor and the duty holder, may affect insurance coverage, and will likely result in observations or failures during any subsequent EICR inspection.