In short: BS 7671:2018+A4:2026 was published on 15 April 2026, and A3 is withdrawn on 15 October 2026. For design calculations, three changes matter most. Reference Method D is split into D1 for ducted cables and D2 for cables direct in the ground. Annex B443 is deleted, so there is no calculated risk level route for surge protection. And Appendix 17 is deleted, with energy efficiency now in Part 8.
This is not a full list of everything Amendment 4 changed. It is the set I had to build into CurrentProof's calculations, where getting it wrong changes an answer. The amendment's headline additions, including the new chapter on stationary secondary batteries, functional earthing for ICT equipment, power over Ethernet and the revised Section 710 for medical locations, are outside its scope. For everything else, the printed amendment is the reference.
1. Buried cables: Method D is now D1 and D2
Tables 4D4A, 4E4A, 4H4A and 4J4A no longer carry a single Method D column.
D1: in ducting in the ground. Installation method 70.
D2: direct in the ground. Installation methods 72 and 73.
The D1 figures are the old Method D figures, cell for cell. D2 is new, and generally higher, because a cable laid direct in the soil does not carry the thermal penalty of the air gap inside a duct. A 70 mm² four core copper SWA cable with 90 degree thermosetting insulation, three phase, is 167 A in D1 and 188 A in D2.
What to do: a design that says "Method D" no longer identifies a method in the standard. Check which installation method each buried run actually uses, and re run direct buried runs against D2, where some will come down a cable size. Tables 4B3 and 4B4 give different soil resistivity and depth factors for ducted and direct buried cables, so make sure each run picks up the right one. The full detail, with the corrections, is in Reference Method D No Longer Exists.
2. Surge protection: no calculated risk level route
Amendment 4 deletes Annex B443. Annex A443 went at A2:2022, so the current standard contains no calculated risk level method at all.
What remains is Regulation 443.4.1. Protection against transient overvoltages shall be provided where the consequence could result in serious injury to, or loss of, human life, or in significant financial or data loss. Then: "For all other cases, protection against transient overvoltages shall be provided unless the owner of the installation declares it is not required due to any loss or damage being tolerable and they accept the risk of damage to equipment and any consequential loss."
What to do: a design that omits SPDs on the strength of a calculated risk level no longer has a basis in the standard. Either provide protection, or record the owner's declaration. The declaration is written for "all other cases", so where either consequence in 443.4.1 applies, it cannot be used to omit protection. Regulation 443.4.2 separately asks you to consider protection where equipment is likely to produce switching overvoltages: motors, transformers, capacitor banks, storage units and high current loads.
3. Appendix 17 is deleted
Appendix 17, on energy efficiency, is deleted by Amendment 4. The energy efficiency material now sits in Part 8, as Chapter 81.
What to do: any design template, specification or report that cites Appendix 17 now cites a part of the standard that no longer exists. Search your templates before the next issue goes out.
The deadline
A3 is withdrawn on 15 October 2026. After that, new designs need A4 as their basis. A spreadsheet, template or software package that still offers a single Method D column, a calculated risk level for surge protection, or an Appendix 17 reference is working to an edition that has been withdrawn.
How CurrentProof handles it
CurrentProof works to BS 7671:2018+A4:2026 throughout. Buried runs take D1 or D2 from the installation method you choose. Surge protection follows 443.4.1, with the owner's declaration as the only way to omit it where no consequence applies. Every result cites the edition it was calculated to, and the free calculators show the full working.