The EICR and its observation codes.
An Electrical Installation Condition Report is a periodic inspection of a fixed electrical installation. The codes on it are what everyone argues about, so they are worth knowing precisely.
How often
Rented homes in England need an inspection at least every 5 years, and at the start of a new tenancy. Owner-occupied homes are usually recommended every 10 years, and the inspector can set a shorter interval for the installation in front of them.
C1: danger present
Someone is at risk right now. The inspector makes it safe before leaving, and the report cannot be satisfactory with a C1 outstanding.
C2: potentially dangerous
Not an immediate risk but it could become one. A C2 makes the report unsatisfactory and the remedial work has to happen.
C3 and FI
C3 is improvement recommended, and does not by itself make a report unsatisfactory. FI means further investigation is needed because the inspector could not reach a verdict, and that does make it unsatisfactory.