Every safety observation on an Electrical Installation Condition Report takes exactly one classification code: C1 (danger present), C2 (potentially dangerous), C3 (improvement recommended) or FI (further investigation). The codes come from the model EICR in BS 7671 and the industry reference for applying them is Electrical Safety First's Best Practice Guide 4 (BPG4), Issue 7.4, August 2026. Under BS 7671:2018+A4:2026 only C1 and C2 observations make the report unsatisfactory; C3 and FI are advisory. That is a change from the A2:2022 form, which treated FI as unsatisfactory, and A2 stays valid until it is withdrawn on 15 October 2026. This guide covers what each code means, worked examples, findings that take no code, and writing observations that hold up.
- One observation, one code. If two could apply, BPG4 says give the most serious.
- C1 or C2 anywhere on the report makes the overall assessment unsatisfactory. C3 and FI never do under A4:2026.
- The A4 model form splits the observations into two lists: C1 and C2 items that drive the outcome, and C3 and FI items that do not.
- FI is for a potential safety issue the agreed extent and limitations stopped you resolving, not a way of putting off a code you could have given.
- Three kinds of finding take no code at all: things worth mentioning that are not non-compliances, harmless departures from BS 7671, and myths.
- Make a C1 safe on discovery where practicable and with the client's agreement, and tell them in writing straight away.
What do the four EICR codes mean?
| Code | Meaning | What you tell the client |
|---|---|---|
| C1 | Danger present. Risk of injury exists now. | Remedial action required immediately. Make safe on discovery where practicable. |
| C2 | Potentially dangerous. Not dangerous now, but a fault or foreseeable event would make it so. | Remedial action required urgently. |
| C3 | Improvement recommended. Not dangerous, but putting it right would make the installation safer. | Advisory. Does not affect the outcome. |
| FI | Further investigation required without delay. A possible safety issue you could not classify within the agreed extent and limitations. | Investigate promptly. Advisory on the A4 form. |
The wording matters because the person reading the report is usually not an electrician. A landlord, letting agent or facilities manager needs to know whether to act today, this week or when budget allows. BPG4 exists so that two inspectors looking at the same fault reach the same code, and it was produced with input from the IET, NICEIC, NAPIT and the other bodies whose logos sit on its cover.
How do the codes decide whether the EICR is satisfactory?
Under A4:2026 the rule is simple: any C1 or C2 observation makes the overall assessment unsatisfactory, and C3 and FI observations do not change it. BPG4 adds that with no C1 or C2 observations it would not be reasonable to call an installation unsatisfactory.
The FI change is the one to watch, because a lot of reports issued in the next few months will still be on the A2:2022 form.
| BS 7671:2018+A2:2022 form | BS 7671:2018+A4:2026 form | |
|---|---|---|
| C1 | Unsatisfactory | Unsatisfactory |
| C2 | Unsatisfactory | Unsatisfactory |
| C3 | Satisfactory | Satisfactory |
| FI | Unsatisfactory (per the form's notes) | Advisory, does not affect the outcome |
| Observations layout | One list | Two lists: C1/C2, then C3/FI |
| Valid until | Withdrawn 15 October 2026 | Current |
A4:2026 was published on 15 April 2026. Until 15 October 2026 a report can follow either form, and the report records which amendment the inspection was carried out to. The IET's explanation for separating FI and C3 from C1 and C2 is that it makes clear they do not lead to an unsatisfactory outcome. If you issue an FI on an A2 form before October, the outcome is still unsatisfactory on that form, so describe the item precisely and tell the client what needs investigating. Our guide at Unsatisfactory EICR: What Happens Next (Landlords & Electricians) covers what the client has to do next.
What are typical C1, C2 and C3 examples?
These are paraphrased from the tables in BPG4 Issue 7.4. They are not exhaustive, the person signing the report is responsible for its content, and BPG4 expects you to be able to justify any departure from it.
| Code | Examples from BPG4 |
|---|---|
| C1 | Accessible live parts: a missing circuit-breaker with no blank fitted, a badly damaged accessory, conductors with missing or damaged insulation. Exposed metalwork made live by a fault. Incorrect polarity at the origin. |
| C2 | No reliable means of earthing, or a gas, oil or water pipe used as the earth. No effective main bonding to extraneous-conductive-parts entering the building. A socket-outlet with no earth. No RCD for sockets likely to supply equipment used outdoors, or for a socket circuit in a room with a bath or shower. Zs too high for the device to disconnect in the required time and no RCD on the circuit. A borrowed neutral, a broken ring or a ring cross-connected with another circuit. Insulation resistance below 1 MΩ to earth. Connections showing signs of overheating. |
| C3 | No RCD for a socket unlikely to supply outdoor equipment and not serving a bathroom. No RCD on domestic lighting circuits. Cables less than 50 mm deep in a wall with no RCD and no other protection. A Type AC RCD where a Type A is needed. A combustible consumer unit, not in a non-combustible enclosure, under a wooden staircase or on the only escape route. No AFDD in an HMO, a high-rise residential building, purpose-built student accommodation or a care home. |
Two of the C2 rows generate more argument than the rest. High Zs is a C2 only where there is no RCD giving additional protection on the circuit; with a working 30 mA RCD the disconnection is covered and the observation moves down. Our guide at High Zs Readings: Causes, Checks and How to Fix Them works through the readings before you code. Low insulation resistance is a straight C2 below 1 MΩ, but a reading between 1 MΩ and 2 MΩ is a Table 64 pass that IET Guidance Note 3 says should be investigated rather than coded; see Low Insulation Resistance: Finding the Fault on Site.
For the ten observations that turn up most often on domestic reports, with the code each usually takes, see EICR Fails: The Ten Most Common C1 and C2 Observations.
Which findings take no code at all?
Issue 7.4 names three kinds of finding that should not be coded, and getting these wrong is the fastest way to lose a client's trust.
The first is observations worth mentioning that are not non-compliances, such as a consumer unit fitted high up, or no AFDDs in an ordinary house. Record them in the comments if they help, but they are not C3s.
The second is non-compliances only: departures from BS 7671 that do not give rise to danger and need not be recorded. Old cable colours are the classic case, and so is a plastic consumer unit that is not under stairs or on an escape route. An installation built to an earlier edition is not unsafe simply because it does not meet the current one, and Regulation 651.2 asks you to assess it against the standard in force, noting where it differs, not to fail it for being older.
The third is myths: things that are not non-compliances at all. Rewireable fuses that still protect the circuit properly, circuit-breakers to BS 3871, and sockets without switches are all in this group. Coding a BS 3871 breaker C3 because it is old says more about the inspector than the board.
When should you use FI?
Periodic inspection is not fault-finding. BPG4 says that in a domestic installation you should generally be able to code every observation without further investigation. FI is for a potential safety issue that the agreed extent or limitations stopped you getting to the bottom of, and the extent and limitations are agreed with the client before you start under Regulation 653.2.
The IET gives two examples of FI used wrongly. An unidentified circuit breaches Regulation 514.8.1, so code it: tracing the circuit is remedial work. An insulation resistance reading below 1 MΩ fails Table 64, so code it: finding the cause is fault-finding. In both cases FI would be dodging a decision you had enough information to make.
A legitimate FI looks like this: a limitation agreed with the client meant a section of the installation could not be inspected, and what you could see suggests a possible safety issue there. Record the limitation on the report, code the item FI, and say in the observation what needs investigating and why. For hidden areas that generate FIs regularly, our guide at Loft and Cellar Wiring: EICR Observations and Codes covers loft and cellar wiring, and EICR Sampling and Limitations Explained: Extent, LIM and N/V covers how to agree and record limitations.
How do you write an observation that holds up?
An EICR is a legal document the client may rely on for five years, and in a dispute the observation wording is what gets read. BPG4 and the model form point the same way.
Describe what you found, not the repair. "Main bonding to incoming water service not present" is an observation; "Fit 10 mm² bonding conductor" is a quote. Price the remedial work separately. Write for the person who ordered the report, in plain language, and give the schedule reference (board, way, circuit) so a second electrician can find it without you. Photographs can be attached and make the report far harder to argue with.
Record faults on the distributor's or supplier's intake equipment, but do not let them decide the outcome unless live parts are accessible. Advise the client to report dangerous intake equipment urgently; BPG4 points to the 105 number for the network operator.
Make the recommended date for the next inspection conditional on C1 items being fixed immediately and C2 items urgently. A five-year recommendation with an unresolved C2 is not a recommendation anyone can act on.
Our guide at How to Write EICR Observations That Stand Up has worked wording for the common ones, and Borrowed Neutrals: How to Find, Test and Code Them shows how to describe a borrowed neutral so the reader understands the risk.
How do the codes apply to rented homes?
In England, the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020 require the landlord to have remedial work done within 28 days of the report, or sooner if the report says so, where the report shows the installation is not satisfactory. GOV.UK guidance for landlords says C1 and C2 observations need remedial work, C3s do not have to be acted on, and FI items must be investigated. That guidance dates from November 2025, before A4:2026 made FI advisory, so describe any FI precisely and tell the landlord what it means for their obligations. GOV.UK's current guidance also covers the social rented sector. Our guide at Landlord EICRs in England: what the 2020 regulations require covers the deadlines, and EICR Landlord Requirements in Scotland and Wales (vs England) covers the other two nations.
How Certio helps
Certio produces the EICR, EIC, Minor Works certificate and PAT records on the BS 7671 model forms and turns them into branded PDFs. Photograph the consumer unit and the circuit schedule drafts itself; point the phone camera at a Megger MFT-X1 and the reading goes straight into the schedule of test results, or dictate it while your hands stay on the probes. Suggested observation wording with the regulation reference is there for you to check and confirm. The judgement stays yours; the typing goes. Starter is free for 7 days, then £4.99 a month.