What is a C3 code on an EICR?

C3 causes the most confusion, because people see a code on their report and assume they have failed. The sections below explain why a C3 is advisory, not a defect.

What 'improvement recommended' means

A C3 is the gentlest of the EICR codes. The model report wording is "Improvement recommended." It indicates that something about the installation could be better — usually because standards have moved on since it was installed — but it is not unsafe as it stands.

Electrical standards evolve with each edition of BS 7671. Work that fully complied when it was carried out can later sit below current practice without becoming dangerous. A C3 captures exactly that situation: the installation is safe to keep using, but bringing the item up to current standards would be an improvement. It is advice, not a warning.

The reason this category exists at all is that an EICR is measured against the current wiring regulations, not the ones in force when the installation was built. Without a C3 code, an inspector would have only two options for anything that no longer reflects current practice: ignore it, or treat it as a defect. Neither is honest. Ignoring it would hide useful information from the owner; treating it as a fault would wrongly imply danger where there is none. C3 is the middle ground that lets the report say, in effect, "this is safe, but here is how it could be brought up to date". That is also why C3 items cluster in older homes — they are the visible trace of how standards have advanced since the property was wired, rather than evidence that anything has gone wrong.

Why C3 keeps a report satisfactory

The single most important point about C3 is that it does not fail the report. Only C1, C2 and FI codes make an EICR unsatisfactory. A report can be marked satisfactory while listing several C3 items, and that is entirely normal — particularly in older homes that were compliant when wired but predate some current requirements.

This is why an unsatisfactory result and a list of recommendations are not the same thing. If your report is satisfactory with only C3 codes, the installation has met the safety standard; the C3s are simply a list of optional betterments. There is no statutory obligation to carry them out, and for a privately rented home a satisfactory report with C3 items still satisfies the inspection requirement.

Examples and whether to act

Common C3 observations include:

• No RCD protection on a circuit that was compliant when installed (where it is not otherwise required to a level that would make it a C2).
• The absence of a current-edition feature that has since been recommended but is not mandatory retrospectively.
• Older-style accessories or labelling that function safely but no longer reflect current practice.
• Minor cosmetic or documentation items that improve the installation without affecting safety.

Whether to act is a judgement call. Carrying out a C3 recommendation — adding RCD protection, for instance — genuinely improves the installation and may be worthwhile when you are already having other work done. But there is no obligation, and it is reasonable to leave a C3 unaddressed where the cost outweighs the benefit. What matters is understanding that a C3 is a recommendation, not a fault you have to fix. If anything in your report is unclear, ask the inspecting electrician to explain why each item was coded as it was.

One subtlety worth holding in mind is that the same observation can sit close to the boundary between C3 and C2, and the difference is not cosmetic. The absence of RCD protection is the classic example: depending on what the circuit serves and how it is used, an inspector might judge it a C3 improvement in one home and a C2 potentially dangerous condition in another. That is not inconsistency for its own sake — it reflects a genuine assessment of risk in context. The practical consequence is that a C3 on your report is a considered judgement that the item, in your particular installation, falls on the safe side of that line. If you are minded to leave it, it helps to understand why it was coded C3 rather than C2, because the reasoning tells you how close to the boundary it sits and therefore how worthwhile acting on it might be. In short, two C3 items are not always equal: one may be a marginal betterment you can comfortably leave, while another sits a hair's breadth from a C2 and is well worth addressing at the first opportunity.

When a C3 is worth acting on anyway

Although there is no obligation to address a C3, there are situations where doing so is sensible rather than strictly necessary. Thinking about it in terms of cost, disruption and benefit usually makes the decision straightforward.

A C3 is often worth acting on when:

• You are already having other electrical work done. If an electrician is replacing the consumer unit or rewiring a circuit anyway, adding the RCD protection a C3 recommended may cost little extra and brings a genuine safety improvement.
• The improvement closes a real gap. Some C3 items, such as the absence of RCD protection, sit close to the boundary with C2. Acting on them removes any ambiguity and improves protection against shock.
• You are preparing to sell or let. A report with fewer outstanding recommendations is tidier to hand to a buyer, tenant or their advisers, even though C3 items do not affect the satisfactory result.

Equally, it is entirely reasonable to leave a C3 in place where the work would be disproportionate to the benefit — for example a recommendation that would require significant disruption for a marginal gain. The honest position is that a C3 is a considered recommendation you can weigh up, not an instruction. The report stays satisfactory either way, so the decision is about whether the improvement is worth its cost to you, not about compliance.

Frequently asked questions

Sources & further reading

• Electrical Safety First — EICR codes explained
• NICEIC — homeowner guidance on EICR codes

Figures on this page are typical UK ranges drawn from published sources and depend on your specific property. They are guidance, not a quotation. Legal duties are summarised for guidance — confirm the current position on GOV.UK.