Amendment 4 is the latest update to BS 7671:2018, the IET Wiring Regulations, which set out how electrical installations in UK buildings are designed, built and checked. Its full title is BS 7671:2018+A4:2026, NICEIC says it’s “commonly called the Orange Book”, and it folds Amendment 3 (2024) into the main text.
Amendment 4 dates
- 15 April 2026: published. The IET’s press release says the IET and BSI “have today released Amendment 4 (2026)”, and SELECT’s overview says it was published “for immediate use”.
- 15 April 2026 to 15 October 2026: both versions current. NICEIC says that in those six months “both versions are considered ‘current’”, so an electrician could work to either.
- 15 October 2026: Amendment 4 mandatory. The IET’s Mythbuster 13 puts it in one line: “Amendments 2 and 3 withdrawn and Amendment 4 must be used.” BSI gives the same date.
Work already under way gets some leeway. NICEIC’s answer is that “if it’s been designed before that date, you can complete it to the previous standard, even after 15 October.” A new installation from that date must comply with Amendment 4, according to SELECT.
Your wiring doesn't become unsafe on 15 October
What changed in Amendment 4
The book itself is paywalled, so this list comes from the summaries the IET, NICEIC and SELECT published after it came out. ECA also lists its top changes, though its notes are for members only.
- New Chapter 57, stationary secondary batteries. NICEIC describes it as covering batteries “where the purpose is for electrical storage and supply of electrical installations”. The IET says it covers “bidirectional or hybrid inverters and the suitability of protective devices for two‑way energy flow”.
- Section 551, generating sets, redrafted. New wording on protective devices where energy flows both ways, and on where a generating set connects relative to the circuit protective devices. This is the part closest to plug-in solar, so it has its own section below.
- RCD types (Regulation 531.3.3). A new note says all RCDs connected in series should suit the type of residual current expected from the loads and possible faults, with a new diagram, Fig A53.2.
- Unidirectional and bidirectional protective devices (Regulation 530.3.201). First introduced in Amendment 3 and now consolidated into the main text.
- AFDDs (Regulation 421.1.7). A wording change: “high-rise residential buildings” replaces “higher risk residential buildings”.
- Protected escape routes (new Regulations 422.2.201 and 422.2.202). Cables and other equipment are kept out of fire-fighting shafts and protected stairways, with set exceptions.
- New and revised sections. Functional earthing and bonding for ICT equipment (new Section 545), Power over Ethernet (new Section 716, limiting SELV and PELV to 60 V ripple-free DC in dry locations and 15 V elsewhere), and a major revision of medical locations (Section 710).
- EV charging. AFDDs aren’t required on circuits supplying charging equipment to BS EN 61851 (Regulation 722.421.1.7.201), and RDC protective devices are introduced.
- Energy efficiency (new Chapter 81). Information only. Appendix 17 is removed.
- Inspection reports. On an EICR, the FI code now reads “further investigation is advised”, without the old “without delay”. NICEIC says an FI used to make the installation unsatisfactory: “Under Amendment 4, this is no longer the case.”
What Amendment 4 didn’t introduce
Two related changes came in earlier amendments. Chapter 82, on prosumer installations, came in with Amendment 2 in 2022, according to the IET’s Wiring Matters. Bidirectional protective devices came in with Amendment 3 in 2024, according to SELECT and the June 2026 joint statement from the electrical industry bodies. None of the summaries we read lists a change to Section 712, the solar PV section, though that doesn’t prove it’s untouched.
Does Amendment 4 cover plug-in solar?
Amendment 4 doesn’t include specific rules for plug-in solar, according to the IET’s and trade bodies’ published summaries. None of the IET, BSI, NICEIC, ECA, NAPIT or SELECT summaries lists plug-in solar or socket-connected generation as a topic. SELECT says the joint BSI and IET committee, JPEL/64, finished the text in January 2026, and the government’s final plug-in solar specification came out on 16 July 2026.
The IET’s 24 March 2026 press release says: “These regulations do not determine what consumers may plug in, placing responsibility on households to ensure that their wiring is fit for purpose before introducing any form of local generation.”
How the law joins BS 7671 and plug-in solar
BS 7671 isn’t law in itself. The government’s safety study says it’s “widely used to demonstrate compliance and legal duties under Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR).” The link to plug-in solar runs through SI 2026 No. 848, in force since 27 August 2026. It amends ESQCR regulation 22(1)(c) so that a source of energy which “is part of a low voltage consumer’s installation” must comply with “British Standard Requirements”, while one which “is a plug-in microgenerator” must comply with the Plug-in Solar Device Interim Product Specification. Put simply, a fixed solar system has to meet BS 7671, and a plug-in kit has to meet the specification. That part of the instrument extends to Great Britain.
The Interim Product Specification v2 is to be read alongside BS 7671:2018+A4:2026. Its scope describes a device connected “via a plug connection to a final circuit originally designed for electricity import from the grid according to the BS 7671 electrical standard”, and it excludes “PV systems according to BS 7671 Section 712”, which are conventional installations.
The IET’s position paper adds that BS 1363-1 says “plugs shall not be used for the connection of electrical power generators to socket-outlets”. SI 2026 No. 848 works around that by letting a notified body approve a plug for a plug-in microgenerator that conforms to BS 1363 in every other respect and complies with the specification.
RCDs and the Type A bidirectional advice
On RCDs, the Amendment 4 change the summaries list is the note on RCDs in series. The IET’s position paper says: “Most two-pole RCCBs, for example those in split load consumer units, are inherently suitable for bidirectional use. Many existing RCBOs installed in UK domestic properties may not have been assessed or marked for bidirectional operation.” It also warns that “many legacy RCDs in the UK are of Type AC which are unable to adequately deal with DC currents emanating from electronic equipment, such as inverters”.
Electrical Safety First turns that into advice for households: “we recommend households have at least a Type A bidirectional RCD protecting circuits intended for use with plug-in solar panels. Until these concerns are addressed, homes with Type AC RCDs should not use plug-in solar systems without first upgrading to a minimum Type A bidirectional RCD on those circuits.”
The specification works from the product side. A kit must not adversely affect upstream RCDs, its smooth DC residual current into the mains must stay at or below 5 mA, and users must be told to test the RCBO now and then while the kit is producing power. Our electrical safety guide explains what those devices do, and do I need an electrician? covers when to call one in.
The Section 551.7.2 reference in the specification
Clause 8.3.2 of the specification says that where connecting a product requires changes to the final circuit, the manufacturer must say so and identify it as electrician’s work, “e.g. replacement of the overcurrent protection device of the concerned electric circuit in accordance with BS 7671 Section 551.7.2 for the connection of a plug-in solar device”.
That reference is hard to map onto Amendment 4. 551.7.2 is a regulation, not a section. SELECT’s summary says Amendment 4 redrafted it into a group: 551.7.2.1 requires a generating set to be installed on the supply side of all the protective devices and treats stationary batteries as a generating set, and 551.7.2.2 covers switchgear assemblies where a generating set runs in parallel with another source. SELECT also says Regulation 551.7.1 gains an indent (c) requiring a suitable protective device where energy flow is bidirectional, and an indent (d) which “prohibits the connection of a source to the load side of an RCD under certain conditions”. The summaries don’t spell out those conditions, and we haven’t seen the book’s wording, so we can’t say which part the specification means. If a kit’s instructions say your circuit needs changes, that’s a job for a qualified electrician working from the book. Electricians who want a firm answer on the cross-reference should ask the IET.
AFDDs
Amendment 4 adds nothing on arc fault detection for plug-in solar. NICEIC says AFDDs are required only for socket-outlet circuits rated up to 32 A in four building types: care homes, high-rise residential buildings, houses in multiple occupation and purpose-built student accommodation. It defines a high-rise residential building as “a residential building over 18 metres or in excess of six storeys”. See our HMO and student accommodation guide if you rent in shared housing.
What Amendment 4 means for you
- If you own or rent a home: nothing to do because of the amendment itself. From 15 October 2026, any new electrical work or EICR you commission is done to Amendment 4, and an FI code on the report no longer makes it unsatisfactory.
- If you’re buying plug-in solar: Amendment 4 doesn’t change what you need: a kit verified on the ENA register, with a factory-fitted BS 1363 plug, in a socket on a socket circuit, with the RCD advice above checked. Our guides on how to tell a kit is legal and the certified kit tracker take you through it, and is balcony solar legal? covers the wider law.
- If you’re an electrician: Amendment 4 is the version for new designs from 15 October 2026. A plug-in kit’s compliance is set by the specification through ESQCR, and any testing or modification of the installation is for professional electricians under the distribution code, G98 and BS 7671. Our building regulations page covers Part P and where BS 7671 sits.
Frequently asked questions
When was BS 7671 Amendment 4 published?
On 15 April 2026, by the IET and BSI together. Its full title is BS 7671:2018+A4:2026, and it could be used from the day it was published.
When does Amendment 4 become mandatory?
On 15 October 2026. The IET says Amendments 2 and 3 are withdrawn that day and Amendment 4 must be used. An installation designed to the previous version before then can still be completed to it.
What are the main changes in BS 7671 Amendment 4?
A new Chapter 57 on stationary batteries, a redrafted Section 551 for generating sets, a new note on RCD types, new sections on ICT functional earthing and Power over Ethernet, a revised medical locations section, escape route rules and EV charging clarifications. An FI code also no longer makes an inspection report unsatisfactory.
Does BS 7671 Amendment 4 include rules for plug-in solar?
Not specific ones, according to the IET's and trade bodies' published summaries. The text was finished in January 2026, before the government's plug-in solar specification existed. A plug-in kit has to meet that specification, which is to be read alongside BS 7671:2018+A4:2026.
Do I need to upgrade my wiring because of Amendment 4?
Not because of the amendment itself. SELECT's summary says an installation to an earlier version of BS 7671 is unlikely to comply with the latest, and that this doesn't mean it's unsafe or has to be upgraded. New work and inspection reports from 15 October 2026 are done to Amendment 4.
What kind of RCD do I need for plug-in solar?
Electrical Safety First recommends at least a Type A bidirectional RCD protecting any circuit used for plug-in solar, and says homes with Type AC RCDs should upgrade those circuits first. The product specification also limits the DC residual current a kit may put into the mains to 5 mA, so it doesn't upset the RCD protecting the circuit.