BS 7671:2018 + A4:2026 · The Orange Book
NEW 18th Edition Wiring Regulations — ‘Deep Dive’
Every material change from A3:2024 to A4:2026, with regulation numbers, what has actually changed on paper, why it matters on site and worked examples. This is the reference version — the shorter cross-amendment summary lives on the BS 7671 Amendments page.
Published
15 April 2026
A3 withdrawn
15 October 2026
Applies to
New work + alterations
Why A4 is a bigger deal than A3
A3:2024 was a short free corrigendum — mostly housekeeping and the new bidirectional-protection definitions. A4:2026 is a paid, fully consolidated second edition (the Orange Book) — it absorbs A1, A2 and A3, adds the new Chapter 57 on stationary batteries, adds new sections (545 and 716), revises Section 710, updates Section 551 and clarifies assemblies, RCD selection, concealed cables, AFDDs and outdoor lighting. Separate scheme competence rules should be checked against the current EAS, not inferred from BS 7671.
New chapter · headline change
Chapter 57 — Stationary secondary battery installations
The first dedicated battery chapter in BS 7671 history. Applies to permanently installed secondary batteries whose primary purpose is electrical energy storage — domestic BESS paired with solar PV, commercial storage, grid-connected arrays and V2H / V2G configurations. It does not apply to pluggable UPS units, BS 5839 fire-alarm batteries, BS 5266 emergency-lighting batteries, or central safety power supplies.
A3:2024 position
No dedicated chapter existed. Designers relied on PAS 63100, MCS guidance, manufacturer instructions and scattered rules in Section 551 (LV generating sets). Bidirectional protection was recognised in A3 through new definitions, but the installation rules sat outside BS 7671.
A4:2026 change
A new Chapter 57 gathers all stationary-battery requirements in one place. Under 551.7.2.1, stationary batteries are considered a generating set, not a load, for the purposes of the Regulations.
Regulations affected
- Chapter 57 — includes requirements for battery location, installation and protection; consult the current PAS 63100 and the manufacturer's instructions when assessing domestic locations.
- 551.7.1 (redrafted) — new indent (c) requires a suitable protective device where energy flow is bidirectional; new indent (d) prohibits connecting a source to the load side of an RCD under certain conditions.
- 551.7.2.1 — the generating set is to be installed on the supply side of all protective devices, and stationary batteries are considered a generating set, not a load, for the purposes of the Regulations.
- Chapter 57 (new) — selection and erection, protection against shock and fault current, isolation, identification and notices for stationary secondary batteries.
What this changes on site
- Every protective device on a battery circuit must be rated for bidirectional flow — many legacy MCBs and RCDs are not.
- Loft installs common in retrofits from 2020–2024 may need revisiting: batteries must not compromise the means of escape.
- Isolation procedures now assume the BESS is a continuous energy source. Provide a dedicated, labelled DC isolator plus AC isolator, and document safe-isolation steps for maintainers.
- Ventilation must match the chemistry — Li-ion needs thermal management; lead-acid needs hydrogen dispersal.
- On periodic inspection, assess battery installations against applicable safety requirements and the condition actually observed; do not assign a code solely because an older installation lacks evidence of compliance with a later edition.
Worked example
Retrofit example — 5 kWh Li-ion battery added to a domestic solar PV system
Check the proposed location against Chapter 57, PAS 63100 and the manufacturer's instructions. Design and document the AC/DC protective devices and suitable means of isolation, taking account of possible power flow in both directions; record the installation and handover information appropriate to the equipment.
Watch out
Bidirectional RCD trap
A common A3-era mistake is connecting a battery inverter to the load side of a household RCD. A4 explicitly restricts this — the RCD may not correctly detect residual current when energy flows from the battery back toward the source. Feed battery circuits from their own dedicated protective device.
New section
Section 716 — Power over Ethernet (PoE) and ELV DC distribution
PoE has become the standard delivery mechanism for LED lighting drivers, IP cameras, access control, BMS sensors and small appliances. Until A4, BS 7671 was silent on it.
A3:2024 position
PoE installations were covered only by the generic SELV / PELV limits (50 V AC, 120 V DC), BS EN 50174 structured-cabling standards and BS EN 62368-3 for the power source. Cable bundle heating in dense patch-panel installs was left to designer discretion.
A4:2026 change
Section 716 covers ELV DC power over balanced ICT cables: permitted sources and voltage limits, a 750 mA per-conductor design-current limit, overcurrent protection, and selection and erection of equipment.
Regulations affected
- 716.414.1.1 — the source must be either power sourcing equipment (PSE) to BS EN 62368-1 and BS EN 60950-22 plus the ISO/IEC/IEEE 8802-3 interoperability requirements, or a source to Regulation 414.3 not exceeding 60 V ripple-free DC in dry conditions and 15 V ripple-free DC in all other locations.
- 716 — wiring may be Category 5 up to Category 8.2 or other balanced ICT cabling; the design current in any conductor shall not exceed 750 mA.
- 716 — also covers protection against overcurrent and selection and erection of equipment; check the full section for inspection and testing detail.
What this changes on site
- High-power PoE requires attention to conductor loading, cable bundling, connector ratings and the selected source's voltage limits.
- Bundled cable derating matters: a rack of 24 patch cords all carrying 90 W runs hot. Space the bundles or upsize conductor CSA.
- Re-using existing Cat 5e panels for PoE++? Assess conductor CSA, connector plating and patch-panel terminal ratings before energising.
- Where PoE distribution is within the agreed scope of an inspection, assess its supply, cable suitability and installation conditions.
Background
Why the 15 V limit outside dry locations?
The voltage permitted for a source under Regulation 716.414.1.1 depends on whether the location is dry. Check the full source and special-location requirements before selecting equipment.
New section
Section 545 — Functional earthing for ICT systems
Modern ICT infrastructure needs both protective earthing (shock protection) and functional earthing (signal integrity and EMC). Before A4 there was no dedicated BS 7671 framework, which caused disputes over separate ICT earth electrodes, dirty-earth conductors and their interaction with PE.
A3:2024 position
Only generic Chapter 54 rules on protective earthing plus BS EN 50310 for telecoms bonding. FE / PE distinction was inconsistently applied on site.
A4:2026 change
Section 545 formalises functional earthing terminology, sets a minimum CSA for FE bonding conductors and mandates identification so FE conductors cannot be confused with PE conductors.
Regulations affected
- 545 — interruption of functional earthing shall not compromise or affect the protective earthing under any circumstance.
- 545 — minimum CSA specified for functional bonding conductors.
- 545 — FE conductors shall be clearly distinguishable from PE conductors.
- 545 — introduces the main functional earthing terminal (MFET), the ICT counterpart of the MET.
- 545 — equipotential bonding ring conductors permitted for data centres and broadcast environments.
- 545 — combined PE/FE conductors permitted with specific CSA and identification requirements.
What this changes on site
- Never lift the FE to chase a hum without knowing whether PE integrity depends on it — with combined PE/FE conductors it does.
- Data centres and broadcast facilities can use ring conductors to hold a consistent reference potential across racks.
- Green-and-yellow is reserved for protective conductors (CPC, MET, bonding). Functional earth conductors are identified with pink sleeving or terminal markings so they cannot be confused with protective earths.
- School and hospital installs with structured cabling co-located with LV panels benefit most: MFET provides a defined interface between the two systems.
Major revision
Section 710 — Medical locations
The most substantive revision of any existing section in A4. Fully aligned with IEC 60364-7-710:2021 and its CENELEC adoption.
A3:2024 position
Group classifications existed but were less prescriptive; medical IT system rules were present but the supplementary bonding test schedule was implicit rather than mandated.
A4:2026 change
Revised Group 0/1/2 classifications; Group 2 requirements sharpened around medical IT systems, insulation monitoring devices (IMDs), dual supplies, UPS placement and a new supplementary bonding resistance test schedule.
Regulations affected
- 710 — Group 0: no medical electrical equipment used on patients (waiting rooms, offices).
- 710 — Group 1: equipment used on intact skin or in non-cardiac procedures (examination, physio, minor treatment).
- 710 — Group 2: interruption of supply could be immediately life-threatening (operating theatres, ICU, cardiac catheterisation, angiography).
- 710 — medical IT systems in Group 2 locations require the specified insulation monitoring and fault-response arrangements; verify the circuit's particular requirements.
- 710 — two independent supplies mandatory for Group 2 to eliminate single-point failure.
- 710.313.1.102 — locate UPS equipment with regard to continuity of supply during fire and separation from risks posed by batteries and power-conversion equipment.
- 710 — supplementary bonding resistance measurements must be recorded in commissioning and every periodic report.
What this changes on site
- Re-survey existing hospital areas: a room previously classified Group 1 may become Group 2 if the procedures carried out there have changed.
- Every commissioning pack for a Group 2 room now needs a signed schedule of supplementary bonding resistance values, not just a tick-box.
- Review UPS siting against the fire strategy and continuity-of-supply requirements rather than assuming proximity to the clinical room is always safest.
New chapter · framework
Chapter 81 — Energy efficiency (introductory)
A new introductory framework aligning LV installation design with the UK's net-zero trajectory. Advisory today, but signals direction of travel for future editions.
A3:2024 position
Energy efficiency guidance sat in Appendix 17 only, and was rarely used as a design input.
A4:2026 change
Not confirmed by the SELECT overview, the IET/EDA briefing or the eFIXX top-ten review — check against the printed text before relying on this. Reported change: an advisory Chapter 81 framework covering load profiling, transformer sizing, power factor correction, conductor selection and circuit layout for efficiency.
Regulations affected
- Chapter 81 (reported, unverified) — framework for assessing energy efficiency at design stage.
- Appendix 17 — energy-efficiency guidance (verified as the existing home of this material).
What this changes on site
- Treat this section as provisional until checked against the Orange Book itself.
- Appendix 17 remains the verified reference for energy-efficiency guidance.
Clarification
Regulation 521.5.1 — Ferromagnetic enclosures
Clarifies grouping of line, neutral and PE conductors through steel enclosures to prevent eddy-current heating.
A3:2024 position
The general rule required all live conductors of the same circuit to pass through the same aperture. Practical exceptions for large busbar assemblies were unclear.
A4:2026 change
Not confirmed by the SELECT overview or the IET/EDA briefing — check against the printed text. Reported change: a note for switchgear and controlgear complying with BS EN IEC 61439, conductors carrying up to 200 A may pass through separate apertures. Above 200 A through separate holes, a temperature-rise test must confirm safe operation.
Regulations affected
- 521.5.1 (reported note, unverified) — 200 A threshold for BS EN IEC 61439 assemblies with separate apertures.
What this changes on site
- Panel builders no longer need to bend geometry to force >100 A conductors through the same hole — provided the assembly is BS EN IEC 61439 compliant.
- Above 200 A per separate aperture, obtain and file the temperature-rise test evidence with the O&M pack.
Clarification
Regulation 521.10.202 — Cable support in fire conditions
Widely misapplied since A2. A4 clarifies the intent.
A3:2024 position
Some inspectors read 521.10.202 as demanding fire-survival cable support on every circuit — even outside escape routes — which was never the intent.
A4:2026 change
An informative note clarifies that the intention is to prevent the general collapse of wiring systems in a fire such that it would hinder safe evacuation, rescue or firefighter access. It is not a requirement for circuit integrity of general wiring. Circuit-integrity requirements for safety services remain in Chapter 56, BS 5839, BS 5266 and BS 8519.
Regulations affected
- 521.10.202 (note added) — clarifies scope: escape and firefighting, not general circuit integrity.
What this changes on site
- Plastic cable clips are still not adequate on cables running along escape routes or above them.
- Support wiring systems so that premature collapse in a fire cannot hinder escape or firefighting; the requirement is not limited to escape routes.
Revision
Section 537 — Firefighter's switches
Formalises collaboration between electrical designers and fire engineers.
A3:2024 position
537.4.2 gave general siting rules; 537.4.2.1 added supplementary detail.
A4:2026 change
537.4.2 is redrafted to require firefighter's switches in locations specified by the fire engineer to support the building's overall fire strategy, with examples such as outdoor lighting at high voltage and indoor discharge lighting at low voltage.
Regulations affected
- 537.4.2 (revised) — location determined by fire engineer within the fire strategy.
- 537.4.2.1 — reported as deleted; not confirmed by the SELECT overview.
What this changes on site
- Get the fire engineer to sign off switch locations before first fix — retrofitting is expensive.
- Document the fire-strategy reference on the EIC.
Revision
Section 551 — Low-voltage generating sets
Reflects the reality of bidirectional energy systems and connects with the new Chapter 57.
A3:2024 position
A3 introduced bidirectional definitions but left the protection wording ambiguous.
A4:2026 change
551.7.1 is redrafted to require a suitable protective device wherever bidirectional flow is possible, with a new prohibition on connecting a source to the load side of an RCD under certain conditions. 551.7.2 is redrafted as a group: 551.7.2.1 (supply-side connection; batteries treated as generating sets) and 551.7.2.2 (LV switchgear assembly rating when a generating set runs in parallel, with four options for the assembly's rated current). Battery requirements now sit in the new Chapter 57.
Regulations affected
- 551.7.1 — redrafted for bidirectional protection.
- 551.7.2 — redrafted as a group, including 551.7.2.1 and 551.7.2.2.
- 551.8 — reported as deleted with content moved to Chapter 57; not confirmed by the SELECT overview.
What this changes on site
- Any inverter capable of exporting must be considered a source — protection must be evaluated in both directions.
- Update template designs for solar PV + battery to reference Chapter 57 alongside 551.
Revision · affects every EICR
Chapter 65 — Inspection & testing (EICR)
Direct impact on every electrician issuing periodic inspection reports.
A3:2024 position
Photographic evidence was widely used but not formally acknowledged. Different scheme providers had different rules about whether an FI code forces an Unsatisfactory outcome.
A4:2026 change
Photographic and thermographic images may be appended as supporting evidence. Recipient guidance based on the Appendix 6 model must be included. Signatures required from both inspector and authoriser. An FI code does not automatically cause an Unsatisfactory outcome — overall condition must be assessed on its merits.
Regulations affected
- Chapter 65 — EICRs must include recipient guidance based on the Appendix 6 model.
- Chapter 65 — photographic and thermographic evidence formally permitted.
- Chapter 65 / Appendix 6 — check the model report's declarations and signatures for the roles involved.
- Chapter 65 — FI code does not automatically drive an Unsatisfactory result.
What this changes on site
- Update EICR report templates to include recipient guidance and the applicable declarations and signatures.
- Keep thermal-imaging camera stills alongside written observations — they are now formal evidence.
- If issuing an FI code, record the reasoning for the overall Satisfactory / Unsatisfactory decision separately.
Worked example
FI example — worn socket outlet on ring final
If an observation needs further investigation, explain what remains unknown and assess the overall installation condition on the evidence available. An FI code does not automatically make the report Unsatisfactory, but it must not be used to dismiss a suspected danger.
Data update
Appendix updates — buried cables in ducts
New current-carrying capacity and volt-drop data for cables installed in buried ducts.
A3:2024 position
Designers had to use conservative reference-method assumptions for buried ducted cables, often oversizing conductors.
A4:2026 change
Dedicated tables added for buried-in-duct installation methods, enabling more accurate sizing and volt-drop calculations.
Regulations affected
- Appendix 4 — new tables for buried cables installed in ducts.
- Appendix 4 — updated volt-drop data supporting the new methods.
- 522.8.10 (note added) — appropriately rated underground conduit or duct with an N750 classification (normal impact, 750 N compression resistance) is recognised as providing mechanical protection equivalent to earthed armour or a metallic sheath.
What this changes on site
- Long sub-main runs to detached garages, workshops and EV chargers can now be sized without the previous over-conservative penalty.
- Re-run your voltage-drop calculations for buried ducted feeds — you may drop a conductor size.
- N750 does not mean SWA is banned, and it is not a burial-depth figure — cable suitability, depth, route identification and current-carrying capacity still need assessment. Check the duct's markings and specification before relying on it.
Industry-wide change
Individual competence — separate scheme requirements
The Electrotechnical Assessment Specification (EAS) governs scheme assessment separately from BS 7671. Check the current EAS for category-specific competence requirements.
A3:2024 position
BS 7671 sets installation requirements; qualifications and scheme-assessment criteria are addressed by the separate EAS and scheme rules.
A4:2026 change
Individual competence requirements are set by the current Electrotechnical Assessment Specification and scheme rules, not by a new BS 7671 regulation. Check the specific qualification and experience requirements for each work category.
Regulations affected
- Electrotechnical Assessment Specification (EAS) — individual competence requirement.
- Check the current EAS and the relevant scheme's inspection-and-testing competence criteria; do not assume one named course is the only route.
What this changes on site
- Confirm that each person doing specialist work has the competence required by the relevant scheme and work category.
- Check which qualifications and experience your registration scheme recognises for each category of work.
- Keep qualification and experience evidence available for scheme assessment.
Revision
Section 722 — EV supply equipment
Builds on the Section 722 framework introduced by A2.
A3:2024 position
722.411.4.1 permits PME earthing where open-PEN detection cuts the L+N+PE within 5 s at ≥ 70 V rms, or where the installation uses a TT arrangement. Practical wording around bidirectional (V2H / V2G) chargers was thin.
A4:2026 change
Section 722 is updated to align with Chapter 57 and Section 551 for bidirectional charging. Open-PEN protection remains the primary mitigation. Documentation requirements for V2H / V2G installations are formalised.
Regulations affected
- 722 — bidirectional EV chargers treated as generating sets and cross-referenced to Chapter 57.
- 722.411.4.1 — open-PEN detection thresholds retained.
What this changes on site
- Standard 7 kW home chargers largely unchanged in practice — most already use O-PEN protection or a dedicated earth rod.
- V2H / V2G installs now attract Chapter 57 obligations if a battery is present.
Revision
Assemblies, multiple supplies and load curtailment
Electrification means consumer units and distribution boards increasingly see current from more than one source — the network plus PV, batteries or V2H chargers — and feed chunky new loads such as EV chargers and heat pumps.
A3:2024 position
Design leant on diversity assumptions and the service-fuse rating. The possibility of an inverter adding current into an assembly was largely left to designer judgement.
A4:2026 change
Requirements around assemblies and multiple supplies are developed, including how the current flowing through each part of a consumer unit or distribution board is considered. Load curtailment — actively reducing or disconnecting loads by intelligent control — is recognised as a design measure, and is distinct from diversity.
Regulations affected
- Load curtailment is an active control measure that reduces or disconnects loads to prevent an assembly or supply rating being exceeded; diversity is only a design assumption about likely usage — the two are not interchangeable.
- For a board supplied by both the network and an inverter, the service fuse alone does not describe every possible current path — check the currents through each part of the assembly against the manufacturer's ratings and instructions.
What this changes on site
- Where the design relies on load control, that control must actually enforce the limit the design assumes — document it in the design paperwork.
- Smart energy management is moving from an accessory towards part of the electrical system design — expect it on EV + heat pump + battery jobs.
Clarification
RCD selection and coordination
Power electronic loads — EV chargers, solar PV, batteries, variable-speed drives, heat pumps — produce residual currents that a basic Type AC device may not detect correctly.
A3:2024 position
RCD selection often began and ended with '30 mA'. The growing variety of Type AC, A, F and B devices was acknowledged but guidance on coordination was thin.
A4:2026 change
Further clarification around RCD selection and coordination: consider what equipment is connected downstream, the type of residual current it may produce, and how one RCD interacts with another in series.
Regulations affected
- Review devices in series as well as the one nearest the load — a suitable downstream RCD does not automatically make the upstream device suitable for the residual currents it may encounter.
What this changes on site
- Check the device markings — the type letters on the front of the device are there for a reason.
- Fitting whatever is cheapest on the wholesaler's shelf is not a robust design strategy for installations with power electronics.
Clarification
Table 52.1 — Cables concealed in walls and partitions
Anyone who has jumped between regulations to work out the rules for cables concealed in walls will welcome this one.
A3:2024 position
The requirements were scattered: prescribed zones, cable depth, mechanical protection and additional RCD protection each lived in different places.
A4:2026 change
New Table 52.1 brings the requirements for cables concealed within walls and partitions into one reference, considering the construction of the wall, whether metallic parts are present, cable depth, prescribed zones, mechanical protection and additional RCD protection.
Regulations affected
- Table 52.1 (new) — consolidated reference for cables concealed in walls and partitions.
What this changes on site
- The rules themselves are not radically reinvented — they are significantly easier to navigate.
Clarification
Conductor class and terminations
Battery storage, EV charging, renewables and industrial equipment mean electricians increasingly terminate fine-stranded conductors, not just solid or stranded building wire.
A3:2024 position
Conductor class was rarely an explicit design consideration when choosing a termination.
A4:2026 change
The need to consider conductor class when selecting a termination is made more explicit — solid Class 1, stranded Class 2, and the increasingly common flexible Class 5 and Class 6 conductors.
Regulations affected
- The terminal must be suitable for the conductor, or the conductor end needs appropriate treatment — a screw tightened onto a bundle of fine strands is not necessarily an acceptable connection.
What this changes on site
- Ferrules and crimped terminations form part of a reliable connection in the right application — but a ferrule is not a universal fix for an unsuitable terminal.
- Check the terminal specification and tightening instructions before terminating Class 5/6 conductors.
Terminology change + EV clarification
AFDDs — high-rise wording and the EV exemption
AFDDs remain required for relevant single-phase AC final circuits supplying socket-outlets rated up to 32 A in specified residential premises.
A3:2024 position
The requirement applied to 'higher-risk residential buildings', houses in multiple occupation, purpose-built student accommodation and care homes; recommended elsewhere. Whether an EV circuit needed an AFDD was ambiguous.
A4:2026 change
The term 'higher-risk residential buildings' changes to 'high-rise residential buildings'. The HMO, student accommodation and care home requirements remain, and AFDDs remain recommended for relevant socket-outlet circuits in other premises. A new clarification states AFDDs are not required for circuits supplying EV charging equipment conforming to the BS EN 61851 series with socket-outlets or vehicle connectors to BS EN IEC 62196-2.
Regulations affected
- 421.1.7 — 'higher-risk residential buildings' becomes 'high-rise residential buildings'.
- 722.421.1.7.201 (new) — AFDDs not required for circuits supplying EV charging equipment to BS EN 61851 with connectors to BS EN IEC 62196-2.
What this changes on site
- The EV exemption is not a blanket pass for any socket somebody might charge a car from — confirm the equipment and connector meet the specified standards.
- The other EV protection requirements remain: assess RCD protection, earthing, PEN-fault protection where applicable and the manufacturer's instructions together.
- Check the building category and circuit scope rather than assuming every domestic circuit requires an AFDD — or that none do.
Recognition
Protective Neutral Bonding (PNB)
PNB has long existed on UK distribution networks but sat awkwardly within the traditional TN-C-S and TN-S descriptions.
A3:2024 position
No formal recognition — certificates and design paperwork had no clean way to describe the arrangement.
A4:2026 change
PNB receives clearer formal recognition, presented as a variant of TN-C-S. This matters when adding equipment such as EV chargers, generators, PV or batteries, where the actual earthing arrangement drives the protective measures.
Regulations affected
- PNB — recognised as a variant of TN-C-S.
What this changes on site
- Do not assume PNB removes PME-related considerations for equipment such as EV chargers — confirm the actual arrangement and the distributor's requirements before choosing protective measures.
- The label on the certificate is only useful if it describes what is actually outside the building.
Strengthened
Protected escape routes and firefighting access
An area under increasing scrutiny following wider changes in building and fire safety.
A3:2024 position
Requirements existed but were less explicit about electrical equipment compromising the protected route itself.
A4:2026 change
Requirements around wiring and electrical equipment in protected escape routes and firefighting access routes are strengthened and clarified. The question is not simply whether a cable is fire resistant — designers must also consider whether equipment and wiring installed in those areas could compromise the function of the protected route itself.
Regulations affected
- Protected escape routes and firefighting access routes — strengthened and clarified requirements for wiring and electrical equipment.
What this changes on site
- For contractors working in larger residential, commercial and public buildings, read this area rather than relying on memory of the previous book.
Revision
Outdoor lighting and additional RCD protection
A less headline-friendly change that affects a surprising number of contractors — car parks, communal areas, public spaces and commercial developments.
A3:2024 position
Additional-protection requirements for outdoor lighting were less explicit about equipment accessible to the public.
A4:2026 change
Requirements concerning outdoor lighting and additional RCD protection are revised and clarified, including the treatment of equipment accessible to the public. An exception applies to lighting supplied from a SELV source.
Regulations affected
- Outdoor lighting — additional RCD protection requirements revised, including equipment accessible to the public; SELV-supplied lighting excepted.
What this changes on site
- Check whether the lighting is accessible to the public and whether the additional-protection requirement applies — 'outdoors' alone is not enough information to select the protection.
Housekeeping
Roman numerals are gone
A formatting change that generated surprising conversation when the book first appeared.
A3:2024 position
Indented lists within regulations used Roman numerals — (i), (ii), (iii).
A4:2026 change
Indented lists now use letters — (a), (b), (c) — aligning BS 7671 with the formatting used by other British Standards.
Regulations affected
- Formatting only — no electrical requirement changes.
What this changes on site
- Training materials, guidance and references to individual clauses written against the old numbering will need updating.
- Electrically, your installation will not notice.
Key dates
Amendment 4 timeline
- 15 January 2026IET and BSI sign off A4 content.
- 15 April 2026Orange Book published — voluntary adoption begins.
- 15 April – 15 October 2026Transition period — A3 and A4 both accepted; both C&G exams available.
- 31 July 2026EAL current qualification closes for new registrations.
- 15 October 2026A3 (Brown Book + Amendment 3 PDF) withdrawn. All new installation work must comply with A4. NICEIC requires access to the Orange Book.
- 31 December 2026EAL current qualification closes for certifications.
Sources
Official references
The definitive text is the printed Orange Book from the IET / BSI. Links below point to primary sources used to compile this page.
- IET — BS 7671 product page
- IET — Amendment 4 information hub
- IET & BSI — Amendment 4 press release (15 April 2026)
- Electrical Safety First — A4:2026 pocket guide (PDF)
- SELECT — Overview of A4:2026 requirements (PDF)
- BSI Knowledge — BS 7671:2018+A3:2024/A4:2026
- eFIXX — Amendment 4: the top 10 changes you need to know
- NICEIC — scheme guidance
- NAPIT — scheme guidance
How A4 affects your installation
New work Paul designs from 15 October 2026 onward will be certified to A4:2026. Existing installations remain compliant with the amendment in force when they were designed; an EICR assesses the condition and safety of the existing installation. A difference from today's edition is not automatically a failure or automatically a C3 — coding depends on the actual risks found.
Summaries on this page are for guidance only. Always refer to the current printedBS 7671:2018+A3:2024/A4:2026 for the authoritative wording. No liability accepted for reliance on this summary — see the disclaimer on the calculators page.