Summary

Amendment 4 is the largest change to the 18th Edition since Amendment 2 in 2022. Where Amendment 3 (July 2024) was a single-issue change — Regulation 530.3.201 on bidirectional protective devices for prosumer installations — Amendment 4 touches every part of the book and adds new sections for technologies that barely existed when the 18th Edition was drafted: home battery storage at scale, vehicle-to-grid, and powered data cabling feeding lighting and building services. It also tidies up the inspection and testing paperwork that electricians use every day, and that change will be the one most of the trade notices first.

The six-month overlap period was designed so that jobs designed and priced to A2/A3 before April could be completed and certified to that edition. That window closed on 15 October 2026. From now on the edition box on an Electrical Installation Certificate (EIC), Minor Electrical Installation Works Certificate (MEIWC) or Electrical Installation Condition Report (EICR) should read BS 7671:2018+A4:2026, and scheme providers (NICEIC, NAPIT, ELECSA, SELECT, Stroma) have updated their model forms accordingly. Anyone still carrying a 2022 brown book with the A3 corrigendum tucked inside is now working to a withdrawn standard.

This article sets out what changed, which regulations and appendices moved, what it means on site for domestic and small commercial work, and what it does not mean — in particular, that an existing installation certified to A2 or earlier does not suddenly need remedial work. Where a secondary source gives a regulation number that could not be confirmed against the published standard, it is marked rather than stated as fact. The authoritative text is the book itself, available from the IET and BSI.

Key Facts

Quick Reference Table

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Area Before A4 (A2:2022 + A3:2024) After A4:2026
Edition to cite on certificates BS 7671:2018+A2:2022 (with A3:2024) BS 7671:2018+A4:2026
Battery energy storage Scattered requirements; Reg 530.3.201 (A3) on bidirectional devices New dedicated chapter; battery treated as a generating set; bidirectional protection in 551.7.1
Power over Ethernet Not specifically covered New Section 716; 60 V / 15 V ripple-free DC limits; BS ISO/IEC 11801-1 cabling
ICT functional earthing General requirements only New section on functional earthing and bonding for ICT systems
Medical locations (710) 2018 text Rewritten; Groups 0/1/2; medical IT systems, IMD, dual supplies, UPS
EICR observation codes Single observations table; C3 and FI listed with C1/C2 Two tables: C1/C2 (unsatisfactory) and C3/FI (not unsatisfactory)
FI wording "Further investigation required without delay" "Further investigation" — for items outside the agreed extent/limitations
Signatures One signature block Separate inspector and authoriser blocks
Earthing options on forms TN-C, TN-S, TN-C-S, TT, IT TN-C, TN-S, TN-C-S (PME), TN-C-S (PNB), TT, IT
Buried cable ratings Single buried rating Direct-buried vs in-duct ratings
Photos on EICR Not provided for on model form May be attached to support observations
Recipient guidance with EICR Shorter list 15 items including six-monthly RCD/AFDD test-button checks and SPD indicator check
Energy efficiency Appendix 17 (informative) Chapter 81

Detailed Guidance

Dates, editions and what to put on the certificate

The amendment was published on 15 April 2026 and could be used from that day. The IET and BSI gave a six-month coexistence period during which either edition was acceptable, so that work designed and priced before April could be finished under the edition it was designed to. That period ended on 15 October 2026 with the withdrawal of BS 7671:2018+A2:2022 and the free-standing A3:2024.

Practical consequences:

Stationary secondary batteries — the new chapter

Home battery storage has gone from niche to routine, and the Amendment 3 fix (Regulation 530.3.201, requiring RCDs, RCBOs and other protective devices in prosumer installations to be suitable for bidirectional current) was a stop-gap. A4 adds a full chapter covering:

On site, the two changes most domestic installers will meet are (1) the EIC Schedule of Inspections now has a row for a prosumer's low voltage installation, so you are expected to have inspected the battery/inverter arrangement as part of the certificate, and (2) the earthing arrangement box distinguishes PME from PNB.

Section 716 — Power over Ethernet

A new special location in Part 7 for installations where structured data cabling (Cat 5e/6/6A) carries extra-low-voltage DC to equipment — PoE lighting, access control, sensors, Wi-Fi access points, cameras. The section:

Electricians who install data cabling alongside power — see data cabling and smart home cabling — now have a section of BS 7671 that applies to it when the cabling is delivering power.

Functional earthing and bonding for ICT

Data centres, server rooms and increasingly smart buildings use functional earthing (for signal reference and EMC) that is separate from the protective earthing required for shock protection. The new section sets out how functional earthing conductors and functional equipotential bonding are arranged, how they relate to the protective earthing system, and how they are identified. Table 51 now includes functional bonding conductors and combined protective-and-functional conductors, and a conductor used only for functional bonding must not be marked as a protective conductor. Most domestic electricians will not meet this; commercial and data-cabling contractors will.

Section 710 — Medical locations

A complete rewrite aligning with IEC 60364-7-710:2021. Medical locations are classified by the risk to the patient of a loss of supply or of a fault:

Group Typical locations Key requirements
Group 0 Consulting rooms, offices in a surgery where no applied parts are used General BS 7671 requirements
Group 1 Treatment rooms, wards, dental surgeries, physiotherapy, where applied parts are used externally or invasively but not in a way where loss of supply endangers life Supplementary equipotential bonding, RCD requirements, specified changeover times
Group 2 Operating theatres, ICU, cardiac catheterisation, where loss of supply or a first fault could endanger life Medical IT system via isolating transformer with insulation monitoring device (IMD); two independent supplies; UPS located as close as practicable to the equipment; stringent bonding and changeover times

Dental practices, GP surgeries, vets and private clinics are the places a general electrical contractor meets Section 710. The practice manager will not know what Group their rooms are; the designer has to classify them with the clinical lead.

Appendix 6 — the new EICR

The change the whole trade will notice first. The model EICR form has been redrafted:

For landlords in England, note the mismatch flagged above: the 2020 Regulations and the GOV.UK guidance still treat FI as requiring action within 28 days, so advise landlord clients not to read the softened form wording as "optional". See electrical safety standards private rented sector and landlord certificates.

Earthing arrangements — PME versus PNB

The model forms now split TN-C-S into PME (protective multiple earthing — the ordinary DNO supply where the neutral is earthed at multiple points) and PNB (protective neutral bonding — where the supply neutral is earthed at one point only, typically on a private network or a single-transformer multiple-source arrangement). Regulation 312.2.1.1 and new Figure 3.9B describe PNB. For a normal domestic DNO supply you will still tick PME. You are more likely to meet PNB on a farm, a private estate network or a site with its own transformer. The distinction matters because the open-PEN risk mitigations required for EV charging (Regulation 722.411.4.1) and the limits on exporting a PME earth to outbuildings depend on the actual arrangement — see tncs earthing pme and pme earthing ev charging.

Buried cables — revised Appendix 4 tables

The current-carrying capacity tables for buried cables now distinguish a cable in direct contact with the soil from a cable in a buried duct or conduit, with different ratings. Every SWA run to a garage, garden office or EV charger is affected: a 6 mm² or 10 mm² SWA in a duct may no longer carry what the previous single buried figure allowed. Re-check standard designs rather than relying on a remembered figure. See armoured cable, swa cable glanding and termination and garden room electrical supply sizing.

What has not changed

Frequently Asked Questions

Do I have to bring an installation certified to A2:2022 up to A4?

No. The 18th Edition's own preface states that installations complying with earlier editions are not necessarily unsafe for continued use or in need of upgrading. A4 does not change that. If you inspect such an installation, record non-compliance with the current edition that does not affect safety as C3, and only code C1 or C2 where there is actual danger or potential danger. SELECT and the IET have both restated this for A4.

What happens to a C3 on an EICR now — has it been downgraded?

The classification has not changed; what changed is the form. A C3 ("improvement recommended") never made a report unsatisfactory, but on the old single-table form it sat alongside C1 and C2 and was often misread by landlords and agents as a fail item. The new form puts C3 and FI in a separate table so the overall assessment is clearly driven by C1 and C2 only. The recommendation to the client is the same as it ever was.

I have a brown book with the A3 corrigendum tucked inside — can I keep using it?

Not for new work after 15 October 2026. A3 is incorporated into the A4 text and A2:2022 is withdrawn. You need the A4 book (or a current subscription to the IET's online version) and your certificates should cite BS 7671:2018+A4:2026. Scheme assessors will check the edition cited on sampled certificates.

Does Amendment 4 change what I need for a domestic battery or solar installation?

In substance it formalises what good installers were already doing: protection suitable for bidirectional current, the battery treated as a generating set under Section 551, location and ventilation requirements and fire-risk mitigation consistent with PAS 63100:2024, and a prosumer row on the EIC schedule of inspections. If you have been installing to Amendment 3 plus PAS 63100 and the manufacturer's instructions, the transition is paperwork and checking the new chapter's wording rather than redesign. Confirm the exact chapter and regulation numbers from the book before quoting them on a certificate.

Is there a new 18th Edition qualification?

Awarding bodies (City & Guilds 2382, EAL) issue an updated 18th Edition requirements qualification for each amendment. Most scheme operators expect at least one qualifying supervisor per firm to hold the current-amendment qualification or to have completed an approved update. Check your scheme's current rule; it is a scheme requirement, not a statutory one.

Regulations & Standards