EICR codes explained: C1, C2, C3 and FI

An EICR records every problem the electrician finds as an observation and gives each one a code. There are four: C1 (danger present), C2 (potentially dangerous), C3 (improvement recommended) and FI (further investigation). Any C1 or C2 makes the whole report unsatisfactory. C3s don’t — and on the latest report forms, neither does an FI.

The four codes at a glance

The wording below comes from the model report forms in BS 7671:2018+A4:2026, the current version of the UK wiring regulations (still the 18th Edition — there is no 19th Edition).

C1 — danger present

A C1 means someone could be hurt right now — for example, live parts you could touch because a socket is smashed or a cover is missing from the consumer unit (fuse board).

The electrician should tell you straight away and, with your agreement, make it safe before they leave — usually by switching off and isolating the affected circuit or equipment. That removes the immediate danger, but it isn’t a repair. The circuit stays off until the fault is properly fixed, so if it supplies something essential — the only socket circuit in a kitchen, say — arrange the repair quickly.

C2 — potentially dangerous

A C2 means something could become dangerous if something else went wrong, such as a fault on an appliance. It needs urgent remedial work. Common examples include:

• no main protective bonding — the earth connection that should be clamped to the incoming gas or water pipes;
• sockets likely to be used for equipment outdoors without RCD protection — the safety switch that cuts the power in a fault;
• signs of overheating at connections;
• missing or ineffective earthing.

The code depends on what the inspector finds in your home, so the same issue can be coded differently in different installations.

C3 — improvement recommended

A C3 means part of the installation doesn’t meet the current wiring regulations, but it isn’t unsafe as it stands. Standards move on — Amendment 4 to BS 7671 was published on 15 April 2026 — and an installation that was fine when it was put in can collect C3s as the rules change. Typical C3s include:

• socket circuits without RCD protection, where a C2 isn’t justified;
• a plastic consumer unit under a wooden staircase or on the only escape route out of the home (anywhere else, Electrical Safety First's coding guidance says a plastic board isn't coded at all);
• older-style fittings that are still sound.

C3s don’t make a report fail, and landlords aren’t legally required to act on them. They’re worth planning into your next round of work — especially if you’re refitting a kitchen or replacing the consumer unit anyway.

FI — further investigation

FI means the electrician found something they couldn’t get to the bottom of during the inspection — for example, test results that suggest a hidden fault, or a circuit they couldn’t trace. The wording changed in 2026:

• On reports using the latest forms (BS 7671 Amendment 4), FI means further investigation is advised. It doesn’t affect the overall result on its own.
• On older-format reports (based on the previous version of BS 7671, which is withdrawn on 15 October 2026), FI means investigation is required without delay, and it makes the report unsatisfactory.

Reports stay in use for years, so you’ll see older-format reports for a long time yet. Either way, get an FI looked at promptly — once investigated, it can turn out to be a C1 or C2. If you’re a landlord and the report asks for further investigation, treat it as part of the 28-day work.

How the overall result is decided

To tell which form you have, look at the key to the codes on your report: “further investigation is advised” means the latest form; “required without delay” means an older one.

A worked example

Take a two-bed flat with one consumer unit. The report lists:

1. C2 — a socket on the balcony, likely to be used for equipment outdoors, with no RCD protection.
2. C3 — the consumer unit has a plastic enclosure and sits in the hallway, the only way out of the flat.
3. C3 — some light fittings are an older style but in good condition.
4. FI — one lighting circuit gave a low insulation resistance reading that needs tracing.

The C2 alone makes the report unsatisfactory. On the latest form the FI is advisory; on an older form it would also count against the result. Either way, sensible next steps are to fix the protection for the balcony socket, investigate the lighting circuit, and decide whether to upgrade the consumer unit at the same time — which could deal with the C2 and the first C3 together. See when an EICR says the consumer unit must go.

Can you question a code?

Yes. Codes are the inspector’s professional judgement about your installation, so ask them to explain any you don’t understand — what they found, why it’s coded that way and what fixing it involves. If you’re still unsure, a second opinion from another qualified electrician is reasonable. You should never feel pushed into paying for work you don’t understand.

What to do next

Landlords: if the report is unsatisfactory, the Electrical Safety Standards in the Private Rented Sector and Social Rented Sector (England) Regulations 2020 require the remedial work — and any further investigation the report calls for — to be done by a qualified person within 28 days of the inspection, or sooner if the report says so. You then send written confirmation, with the report, to your tenants and the council within 28 days of the work being finished. See unsatisfactory EICR: what happens next and EICR for landlords.

Homeowners: there’s no legal deadline, but C1 and C2 items are genuine safety risks. Fix them first, get any FI investigated, then plan the C3s.

Tenants: your landlord must give you a copy of the report. If it shows C1 or C2 items, they must be dealt with within 28 days of the inspection.

Common mistakes

• Treating a C3 as a fail and paying for work that isn’t needed yet.
• Ignoring an FI because the report looks satisfactory — it may be hiding a bigger problem.
• Assuming a C1 circuit that has been switched off is fixed.
• Skipping the limitations section, which lists anything the inspector couldn’t reach.

Key points

• C1 and C2 make a report unsatisfactory; C3 never does.
• FI is advisory on the latest forms but counts as unsatisfactory on older ones.
• Landlords must deal with C1, C2 and any required further investigation within 28 days.
• Ask for each code to be explained before you pay for any work.

Get your codes explained

We explain every observation on your report in plain English — what it is, why it matters and what fixing it involves. If anything needs putting right, you get a clear quote for remedial works, with no obligation to use us. You can see how codes appear on our sample report.

Need an inspection? Read about our landlord EICR and homeowner EICR services, see your price — including VAT — before you book, or call us on 07301 010244.