EICR codes C1, C2, C3 and FI: what each one means
5 min read · Updated 28 Sep 2026 · Reviewed by accredited engineer
When an NICEIC electrician performs an Electrical Installation Condition Report (EICR), any observed faults are graded using standardised defect codes: C1, C2, C3 and FI. If your report contains any C1, C2 or FI items, the certificate will be unsatisfactory and remedial work is legally mandatory within 28 days.
Breakdown of observation codes
Understanding the severity of each code ensures you know what requires immediate isolation vs planned maintenance.
Code C1: Danger present. Risk of injury. The engineer will make safe immediately.
Code C2: Potentially dangerous. Urgent remedial work required.
Code FI: Further Investigation required without delay.
Code C3: Improvement recommended (does not cause the test to fail).
The 28-day statutory rule
Landlords have 28 calendar days from the date of an unsatisfactory EICR to complete required remedial work and obtain written proof of compliance.