EICR codes explained: C1, C2, C3 and FI — and what Amendment 4 changed

An EICR comes back with a verdict — satisfactory or unsatisfactory — and a list of observations, each carrying a code. The codes are where the money and the argument live, and they're widely misunderstood in both directions: landlords who think a C3 is a bill, and reports marked unsatisfactory that shouldn't be.

The rules also changed this year. Amendment 4 to BS 7671 was published on 15 April 2026, and from 15 October 2026 the previous edition is withdrawn and A4 is the current one, so at the time of writing both are in use and you may hold reports on either. Some of what follows is different from what the same page would have said last year.

Worth being precise about "mandatory", because it gets thrown around. BS 7671 is a British Standard, not a statute. It is not law in itself; it carries its weight because it is the accepted way of showing compliance with legal duties like the Electricity at Work Regulations, the Building Regulations and, for landlords, the electrical safety regulations that name it directly. Departing from it is not an offence — it just leaves you having to demonstrate, on your own, that what you did was at least as safe.

The four codes

The wording below is from the Amendment 4 model EICR form itself:

• C1 — "Danger present. Risk of injury. Immediate remedial action is necessary."
• C2 — "Potentially dangerous - urgent remedial action is necessary."
• C3 — "Improvement recommended."
• FI — "Further investigation is advised."

Two wording changes came in with Amendment 4. C1 and C2 moved from "required" to "is necessary", and FI moved from "further investigation required without delay" to "further investigation is advised" — a deliberate softening, for reasons in the next section.

Electrical Safety First's Best Practice Guide 4, which is the coding reference most inspectors actually work from, still prints "required" for C1 and C2 while having adopted the new FI wording. So the two documents differ slightly, and neither is wrong. If you're quoting the wording, say which one you're quoting.

One rule that saves arguments: each observation gets one code only. Where more than one could apply, the most serious of them is the one used.

Which codes make a report unsatisfactory

C1 and C2. That's the whole list.

The Amendment 4 form is unusually direct about it. Section E states that an unsatisfactory assessment indicates dangerous (C1) or potentially dangerous (C2) conditions have been identified, and that anything classified C3 or FI is advisory, does not affect the overall assessment, and should be given due consideration.

The form has also been physically restructured to stop people getting this wrong. The observations section is now two boxes rather than one: C1 and C2 observations sit in a box labelled as affecting the overall assessment, and C3 and FI sit in a separate box labelled as not affecting it.

It runs the other way too, which matters more than it sounds. Best Practice Guide 4 states that where a report contains no C1 or C2 observations, it would not be reasonable to report the installation as unsatisfactory. An unsatisfactory verdict has to be earned by a specific finding — it isn't a general impression of an old installation.

FI is the change worth knowing about

Under the previous wording, "further investigation required without delay" read to a lot of people — including plenty of electricians — as a failure. The IET's explanation of the Amendment 4 change is that the codes were decoupled and re-worded precisely so this could not be misread again.

The history behind that is less tidy than it is usually told, and worth knowing if you are looking at an older report. The position under previous editions was genuinely argued over — NICEIC's own guidance treated an Amendment 3 FI as producing an unsatisfactory report — so somebody holding a pre-A4 report marked unsatisfactory on an FI was not necessarily given the wrong answer at the time. What is unambiguous is the position now. For anything on the current form, FI is advisory and does not affect the assessment; for an older report, read it against the edition and the guidance that applied when it was written.

So: an FI does not fail a report.

The trap, and it's a real one

If you're a landlord in England, do not read the paragraph above as "an FI can be ignored".

The overall verdict on the report comes from BS 7671. Your legal duty comes from the Electrical Safety Standards Regulations, which are a different instrument with different triggers, and the government's guidance is explicit that where an inspector identifies that further investigative work is required, the landlord must ensure it is carried out.

Which means both of these can be true on the same report at the same time: the assessment reads satisfactory, and you owe a statutory duty to get the FI investigated within 28 days. The report is not the law, and the two were never designed to line up.

Worth knowing that the government's guidance page still prints the old "further investigation required without delay" wording, so it currently disagrees with the standard on the words while agreeing on the duty.

What each code looks like in practice

Examples below are from Best Practice Guide 4.

C1 — danger present. The pattern is almost always live parts you could touch:

• A protective device missing from a consumer unit with no blanking piece fitted, leaving exposed live parts accessible to touch.
• An accessory badly damaged enough to expose live parts.
• Line or neutral conductors with no insulation, or damaged insulation.
• Terminations or connections with missing or damaged barriers or enclosures.
• Conductive parts that have become live through a fault, or incorrect polarity at the origin of the installation.

C2 — potentially dangerous. Not live-and-touchable today, but one fault or one wrong move away:

• Absence of effective main protective bonding of extraneous-conductive-parts entering the building.
• Absence of a reliable and effective means of earthing for the installation.
• No circuit protective conductor on a circuit supplying Class I equipment, or supplying switches with metallic faceplates.
• No earthing at a socket-outlet.
• Circuits with ineffective overcurrent protection — the classic being a rewireable fuse fitted with oversized fuse wire.
• On a TT system, a main RCD or voltage-operated earth-leakage circuit-breaker that fails to operate when tested.

C3 — improvement recommended. Real findings, no obligation:

• Circuits not identified at the consumer unit — no labelling of which breaker does what.
• A missing "Safety Electrical Connection — Do Not Remove" warning notice where one is required.
• Main bonding that is present and adequately sized but not accessible for inspection.
• No circuit protective conductor where the circuit only serves Class II equipment and is unlikely to be changed.
• A combustible consumer unit under a wooden staircase or in the sole route of escape.

The RCD grading, because "no RCD is a C2" is wrong

This is the single most common coding myth, and the guidance is graded rather than binary:

• C2 — no RCD protection for mobile equipment that could reasonably be expected to be used outdoors.
• C2 — no RCD protection for a socket-outlet in a location containing a bath or shower.
• C3 — no RCD protection for a socket-outlet that is unlikely to supply mobile equipment for use outdoors, doesn't serve a bathroom, and which the inspector doesn't otherwise consider to present danger.
• C3 — no RCD protection for domestic lighting circuits.
• C3 — no RCD protection for cables buried less than 50mm in a wall.

Note what's actually doing the work: what the circuit serves, not whether an RCD exists. And note that the C3 has an explicit judgement clause in it. A ground-floor socket that a lawnmower will obviously be plugged into is a case where the IET has advised C2 is generally appropriate, even though a strict reading of the C3 wording might tempt otherwise. That is genuine competent-person judgement, not a loophole.

The blanking plate, coded three different ways

A neat illustration of why identical-sounding observations get different codes:

• Missing blank, live parts accessible to touch — C1.
• Blank not suitably secured or durable, on a consumer unit without a lockable lid — C2.
• Same insecure blank, on a unit with a lockable lid — C3.
• Absence of internal barriers where the cover can only be removed with a key or tool — not a defect at all.

Two categories most people don't know exist

Best Practice Guide 4 carries two more classifications that never appear on the report:

"NC only" — a non-conformity with BS 7671 that doesn't give rise to danger and isn't recommended for improvement, and which should not be recorded on the EICR at all. Main bonding of 6mm² or more with no thermal damage is one.

"Myths" — items that aren't non-compliances at all and don't need reporting. Rewireable fuses, where they genuinely provide adequate circuit protection, are on that list. So are BS 3871 circuit-breakers. So is bonding to boiler pipework or a metal sink that isn't an extraneous-conductive-part.

That last one is worth dwelling on, because "extraneous-conductive-part" is carrying the entire load in the bonding rules — and it is a question about the whole pipework, not about the bit you can see at the meter.

A plastic incoming service is a good reason to ask the question. It is not the answer to it. Metal pipework fed by a plastic incomer can still be extraneous if it picks up earth potential anywhere else: a buried metal section further along, a connection to earthed plant, an outside tap on a metal run into the ground. The IET's own guidance conditions the plastic-incomer answer on there being no such fortuitous contact, and its "To bond or not to bond" piece works exactly this example. So it has to be established on the installation, by measurement, rather than assumed from the material at the entry point. Where it genuinely is not an extraneous-conductive-part, coding the absence of bonding as C2 is a documented myth rather than a strict reading — but that "where" is doing real work.

Things that are commonly said and are not true

"It doesn't meet the current regulations, so it fails." No. The model form carries a note saying that an installation designed to an earlier edition of BS 7671, and which doesn't fully comply with the current one, is not necessarily unsafe for continued use or in need of upgrading. Age alone is not a defect, and it is not automatically a C3 either — a code goes on the report because of what the finding means for safety, not because the installation is old. Some older-standard features warrant no recorded code at all.

"A C3 has to be fixed." Not by the code. It's a recommendation, and the report passes with any number of them on it. But the code and the law are two different questions, and a C3 does not answer the second one. A Scottish landlord whose installation has no 30mA RCD in the main consumer unit is in breach of the Repairing Standard whether the inspector wrote C3 against it or nothing at all — paragraph D.55 of the statutory guidance is a requirement in its own right, and D.70 says only that C3 work is not necessarily required to meet the standard. The right reading is that a C3 creates no obligation, not that it removes one.

"The customer can tell the inspector what code to use." No. The guidance says plainly that the inspector's judgement should not be unduly influenced by the person ordering the work, and that whoever signs the report is fully responsible for its content and accuracy. A genuine error should be corrected on request; a disagreement about judgement is resolved by paying someone else for a second opinion, not by pressure. There's no formal appeal procedure — if anyone tells you there is, ask them to point at it.

"FI is for anything you're unsure about." This is the one aimed at electricians, and the IET has been pointed about it. An unidentified circuit is a labelling non-compliance to be coded, not an FI — tracing it is remedial work, not part of the inspection. An insulation resistance reading below 1MΩ is likewise something to code. Best Practice Guide 4 gives no examples at all of FI codes applicable to domestic installations, and the IET's position is that it shouldn't be necessary to use one in most circumstances.

What landlords actually have to do

Three different regimes, and they are not variations on one theme.

England. An EICR at least every five years. Where the report requires further investigative or remedial work, it must be done within 28 days of the inspection — or sooner if the report says so — with written confirmation from a qualified person supplied to the tenant and the local housing authority. The maximum financial penalty is £40,000 — raised from £30,000 on 1 November 2025 by the same amendment that brought social housing into scope.

Scotland. The duty sits in primary legislation rather than regulations, which makes it wider. The five-year cycle is statutory, and so is a requirement covering residual current devices specifically. It also covers landlord-supplied appliances as well as the fixed wiring — a second inspection recorded on its own forms and attached to the EICR — and records must be kept for six years.

Wales. A valid report throughout each period of occupation, with a copy to the contract-holder within 14 days of the occupation date. Note that direction of travel: unlike England, the report can arrive after they've moved in. It covers the fixed installation only, with no appliance duty. The consequence of getting it wrong is unusual and severe — the dwelling is treated as unfit for human habitation, which means rent isn't payable for the period and certain notices can't be served, and that follows from missing the paperwork deadline even where the installation itself is perfectly safe.

What an EICR costs and what moves the price covers the money side and the red flags.

For the electricians reading

Two practical notes.

Between now and 15 October 2026 both editions of the standard are live, so you may be handed a report using either FI wording. From 15 October the previous edition is withdrawn. What Amendment 4 changes on your certificates has the form-level detail and the question of whether you need to buy anything.

The second is duller and worth more. The EICR you issue today has a next-inspection date on it, and in five years the electrician who contacts that landlord first gets the work. The certificate is a document you hand over; the date is an asset you keep. Very few people keep it in any form they can search.

grafter.ly isn't certification software and won't produce your EIC. What it does hold is the clock: a job set to come round in five years puts itself back in your list when it's due, with the property and the customer attached. It tells you; you decide whether to contact them. It never emails your customer on your behalf, because a message about a property whose state nobody has checked is a bad thing to send in your name. You can try it free for 30 days, no card to start.

---

Sources. Code wording, the Section E and Section K statements on overall assessment, and the note on earlier editions are from the BS 7671:2018+A4:2026 model EICR form, published free by the IET. Coding examples, the "NC only" and "Myths" categories, the one-code-per-observation rule and the inspector-judgement statement are from Electrical Safety First Best Practice Guide 4, Issue 7.4 (August 2026). The decoupling of C3 and FI from the overall assessment, and the position on overuse of FI, are from IET Wiring Matters issue 110, July 2026; the Amendment 4 dates are from Wiring Matters issue 109, April 2026. England's duties and the FI position are from the GOV.UK guidance and regulation 3; the £40,000 maximum is regulation 11 as amended by SI 2025/1043. Scotland is the Housing (Scotland) Act 2006 s.19A and the repairing standard statutory guidance; Wales is SI 2022/6 regulation 6 and SI 2022/23 regulation 11. All checked 8 September 2026. This is general information, not advice on a specific installation — the codes on your report were assigned by the person who inspected it, and they are the one to ask.