EICR Codes Explained: C1, C2, C3 and FI — What Each Code Means for UK Electricians and Landlords (2026)

The four EICR classification codes

Every observation recorded during an Electrical Installation Condition Report is assigned one of four classification codes. The code tells the property owner, landlord, or tenant how serious the fault is and what action — if any — is legally or practically required. The table below gives a quick-reference summary of all four.

C1 — Danger Present: what electricians must do

A C1 code means the inspector has found a live danger — something that poses an immediate risk of electric shock, fire, or both. This is not a theoretical or future risk; it is a hazard that exists at the moment of inspection. C1 is the most serious of the four codes and requires action before the EICR can be concluded.

An electrician cannot issue a satisfactory EICR with an unresolved C1 outstanding. In practice, there are two paths: the electrician makes the installation safe on the day — for example by isolating the affected circuit, replacing a missing cover, or disconnecting an unsafe connection — and records the remedial action taken. Where making safe is not possible on that visit, the electrician must advise the client in writing to isolate the affected circuit immediately and not use it until the fault is rectified.

Common examples of C1 observations include:

• Exposed live conductors — bare copper wiring accessible to touch, damaged cable insulation exposing live cores, or open junction boxes without covers.
• Missing or inadequate earthing on metalwork — pipework, metallic enclosures, or extraneous-conductive-parts that should be bonded but are not, creating a shock risk if a fault occurs.
• Non-functional RCDs protecting socket circuits — where a residual current device that should provide personal protection fails the trip-time test and cannot be relied upon to disconnect on a fault.

Because a C1 is immediate, it almost always results in the electrician spending additional time on site beyond the original scope. This is usually charged separately. It is also worth noting that a property with a C1 observation cannot legally be let until the fault is rectified and a satisfactory report issued.

C2 — Potentially Dangerous: the 28-day rule for landlords

A C2 code means the fault could become dangerous under foreseeable circumstances, but does not present an immediate risk in the way a C1 does. The installation is still classed as unsatisfactory and the EICR will fail. For landlords, a C2 triggers a specific legal obligation under the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020.

Under those regulations, landlords must ensure that all remedial work identified in an unsatisfactory EICR — including all C2 faults — is completed within 28 days of receiving the report, or within a shorter timeframe if one is specified by the inspector. Once the work is done, the landlord must obtain written confirmation from the electrician who carried out the remediation (typically an Electrical Installation Certificate or a Minor Works Certificate), and must provide copies to tenants and, if requested, to the local authority.

Common C2 observations include overloaded circuits, inadequate overcurrent protection, damaged but not fully exposed wiring, missing RCDs on circuits where they are now required (such as all socket circuits under the 18th Edition), and consumer units that do not meet current fire-containment requirements.

It is worth noting that the 28-day rule applies in England. Scotland, Wales, and Northern Ireland have their own electrical safety legislation for rental properties with slightly different timescales and enforcement mechanisms, though the practical requirement to address C2 faults promptly is consistent across all four nations.

C3 — Improvement Recommended: does it fail an EICR?

No. A C3 is advisory. An installation that receives only C3 observations will still be awarded a Satisfactory overall outcome. The property can be legally let and the landlord has no statutory obligation to act on C3 codes, although electricians recommend addressing them as best practice when budget and timing allow.

C3 observations typically arise when an installation was compliant under an older edition of BS 7671 but does not fully meet the requirements of the current 18th Edition (Amendment 2). The wiring was installed correctly at the time; it has simply not been updated to reflect changes in best practice over the intervening years.

Common C3 observations include:

• Older wiring that meets a previous edition of the wiring regulations — such as PVC twin-and-earth cable installed under the 16th Edition, which remains safe but may not fully comply with Amendment 2 requirements for certain circuit types.
• Absence of SPDs (surge protection devices) — since Amendment 2 came into effect, surge protection is recommended for all new domestic installations. Older properties without SPDs receive a C3 rather than being failed outright.
• Consumer unit without arc fault detection (AFDDs) — AFDDs are now recommended in high-risk locations such as bedrooms in houses of multiple occupation. An older consumer unit without them may attract a C3 in those contexts.

For landlords, a report with only C3 codes means you can continue letting the property without any legal obligation to carry out work. However, if you are already planning other electrical work on the property, it is often cost-effective to address C3 items at the same time, since the electrician is already on site and some of the set-up costs are shared.

FI — Further Investigation Required: what happens next

An FI code is issued when the electrician cannot fully test or assess part of the installation during the visit. This leaves the safety of that element uncertain. Because the overall condition of the installation cannot be confirmed, an FI code results in an Unsatisfactory overall outcome until the investigation is completed and a new or supplementary report is issued.

FI is not a code for faults that are visible and quantifiable — those receive C1, C2, or C3. It is specifically for situations where the electrician has identified a potential issue but cannot determine its severity because of limited access, the need for specialist equipment, or some other constraint that cannot be resolved during the standard EICR visit.

Common FI scenarios include:

• Wiring concealed and inaccessible — suspected damage behind plaster or under floorboards where the cable cannot be reached for visual inspection or testing without causing damage to the fabric of the building. A follow-up investigation may require opening up sections of wall or floor.
• Specialist periodic test required for industrial equipment — some fixed equipment (for example certain medical devices, specialist machinery, or large three-phase plant) requires a specific test methodology that a standard domestic or commercial EICR visit does not cover.
• Circuit that could not be isolated for testing — occasionally a circuit serves equipment that cannot be safely switched off during the inspection visit (for example a server room or a medical refrigerator), meaning the standard insulation resistance test cannot be carried out.

Once the further investigation has been completed, the electrician issues a supplementary report or an updated EICR confirming the outcome of the additional testing. If the FI investigation reveals a C1 or C2 fault, the property remains unsatisfactory and the usual remedial requirements apply. If it reveals no fault, the overall outcome can be revised to Satisfactory.

How codes affect the EICR overall outcome

An EICR produces one of two overall outcomes: Satisfactory or Unsatisfactory. There is no middle ground. The overall outcome is determined by the codes assigned to each observation. The rule is straightforward: any C1, any C2, or any unresolved FI means Unsatisfactory. C3 observations on their own always result in Satisfactory.

For landlords, the practical implication is clear: a Satisfactory report with C3 codes is legally compliant and the property can be let. An Unsatisfactory report — regardless of whether the fault is a C1, C2, or unresolved FI — means the landlord must act before the property can be let or, if it is already tenanted, within the required timeframe set out in the regulations.

What to do if your property has C1 or C2 codes

Receiving an unsatisfactory EICR with C1 or C2 codes does not need to be a stressful situation. Follow these steps to resolve the issue correctly and get back to a compliant property as efficiently as possible.

Related EICR and electrical cost guides

Now that you understand the classification codes, you may want to explore what the inspection itself costs, or what electricians charge for the remedial work needed to resolve C1 and C2 faults.

• →EICR Cost UK 2026 — how much an Electrical Installation Condition Report costs by property size, region, and whether remedial work is needed.
• →Electrician Hourly Rate UK 2026 — day rates and hourly rates for electricians across the UK, including what to expect to pay for remedial work following an unsatisfactory EICR.