EICR codes C1, C2, C3 and FI explained

The four codes at a glance

Every EICR (Electrical Installation Condition Report) ends with a list of observations. Each one gets a code. The codes are set by BS 7671, the UK wiring standard. The version in force since 15 October 2026 is BS 7671:2018+A4:2026, known as Amendment 4.

Code	Meaning	Makes the report unsatisfactory?	Typical action
C1	Danger present. Immediate remedial action necessary.	Yes	Made safe at the visit, then repaired
C2	Potentially dangerous. Urgent remedial action necessary.	Yes	Repair booked straight away
C3	Improvement recommended.	No	Plan it in, often with other work
FI	Further investigation advised.	Not by itself under Amendment 4	Investigate to find out what is behind it

C1: danger present

A C1 means someone could get a shock or a fire could start now. Examples:

• a socket or switch with a cracked or missing cover, exposing live parts
• a ceiling rose with bare live terminals within reach
• a cable with insulation burned or worn through to the copper
• live parts accessible inside a consumer unit with a missing blank

An inspector who finds a C1 will normally make it safe before leaving, for example by switching off and isolating that circuit, and will tell the person responsible. The repair then needs doing.

C2: potentially dangerous

A C2 is not an immediate danger, but would become one if a second thing went wrong. This is the code that most often turns an EICR unsatisfactory. Examples:

• no RCD protection on socket circuits where it is needed (an RCD, residual current device, cuts power within a fraction of a second if current leaks to earth, such as through a person)
• no main protective bonding to the incoming water or gas pipe, or bonding that is too small
• an earth fault loop reading too high, meaning a breaker might not trip fast enough in a fault
• signs of overheating at a terminal or in the consumer unit
• old cable whose insulation is breaking down

Electrical Safety First notes that cables coated in black rubber were phased out in the 1960s. Where that cable turns up and its insulation is crumbling, it is often coded C2.

C3: improvement recommended

A C3 means the installation does not meet today’s standard in some way, but is not considered dangerous. Standards change. Something that was correct when it was installed can be a C3 now. Examples:

• a plastic consumer unit in a home, where new units must now be in a non combustible (usually metal) enclosure
• no surge protection
• labelling missing or out of date
• an older type of socket or switch in good condition

C3 items do not make a report unsatisfactory, and there is no legal deadline to fix them. It is often worth doing them when other work is happening.

FI: further investigation

FI means the inspector found something they could not fully assess during the visit and wants it looked into. Examples:

• a circuit that cannot be traced to where it ends
• an unexpected test reading that needs more time to explain
• a part of the installation that could not be reached

The Amendment 4 change

Before Amendment 4, any FI made the whole report unsatisfactory. NICEIC’s Amendment 4 guidance explains that the observations section is now split in two. The first part holds C1 and C2 items, which decide the result. The second part holds C3 and FI items, which do not. The wording of FI has also changed: it used to say “without delay”, and that has been removed.

NICEIC says the reason is that FI was sometimes used where not enough time had been allowed for the inspection, or as a way to come back for more work without evidence. The change is meant to make reports more accurate.

For landlords, read this alongside the law. The government guidance says remedial or further investigative work shown as necessary in the report must be done within 28 days. So an FI is still something to book, even if the report is satisfactory.

A worked example

Picture a Victorian terrace converted into two flats, the kind found across Hackney and Wandsworth. The lower flat’s EICR might read:

• C2: socket circuit in kitchen not RCD protected
• C2: main bonding to gas pipe missing
• C3: plastic consumer unit
• C3: no surge protection
• FI: lighting circuit 3 could not be traced fully, may pass through upper flat

Result: unsatisfactory, because of the two C2 items. The landlord needs both C2s repaired, and the FI investigated, within 28 days. Often the fix for the first C2 is a new consumer unit with RCD protection, which also clears the plastic board C3. That is notifiable work under Part P. See our consumer unit replacement page, and our Hackney page for more on converted flats there.

Reading your own report

1. Turn to the summary and check the overall result.
2. Read every observation and its code.
3. Ask the inspector to explain anything you do not understand, in plain terms.
4. Ask for written prices for C1, C2 and FI work.
5. If you are a landlord, follow the steps in EICR unsatisfactory: what next.

Our EICR page explains how we carry out inspections and price repairs after the report.