Periodic inspection assesses whether an existing electrical installation is safe for continued use. The result is an EICR — the most common certificate UK electricians produce. This guide covers the full procedure: when to inspect, how much to test, how to record limitations, and how to classify defects.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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A periodic inspection is a systematic examination and testing of an existing electrical installation to assess its condition and safety. Unlike initial verification (which certifies new work), a periodic inspection evaluates an installation that is already in service — often one that has been in use for years or decades.
The purpose is to identify any defects, deterioration, or non-compliance that could pose a risk of electric shock, fire, or injury. Electrical installations age, components degrade, connections loosen, and insulation breaks down over time. A periodic inspection catches these issues before they become dangerous.
The outcome of a periodic inspection is an Electrical Installation Condition Report (EICR) — a standardised document that records the condition of the installation, lists all observations and defects with classification codes, and gives an overall assessment of Satisfactory or Unsatisfactory. The EICR model form is specified in Appendix 6 of BS 7671.
Periodic inspection and testing is covered by Chapter 65 of BS 7671 (which replaced the former Chapter 62 in the 18th Edition) and is supported by GN3 (Guidance Note 3: Inspection and Testing, 9th Edition).
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A periodic inspection should be carried out:
IET Guidance Note 3 provides the following general recommendations for maximum intervals between periodic inspections:
These are maximum recommended intervals. The inspector may specify a shorter interval based on the condition of the installation, the environment, and the type of use. If the installation is in poor condition, a 3-year or even 1-year interval may be appropriate regardless of the installation type.
The core test sequence is the same for periodic inspection as for initial verification: dead tests first, live tests second. However, there are important practical differences:
The dead-before-live sequence still applies: isolate each circuit, perform dead tests, re-energise, perform live tests. In practice, many inspectors batch the work — isolate a group of circuits, perform all dead tests on that group, then re-energise and do all live tests.
Sampling is one of the key differences between periodic inspection and initial verification. IET Guidance Note 3 (GN3) allows representative sampling during periodic inspection, with detailed guidance on sample sizes:
Practical tip: For a typical domestic property with 6 to 10 circuits, 100% testing is usually faster than deciding which circuits to sample. Sampling is most useful on larger commercial or industrial installations with dozens of similar circuits (for example, 50 identical lighting circuits in an office building).
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Every periodic inspection has limitations — areas that could not be fully inspected or tested. This is normal and expected. The key is to record every limitation clearly on the EICR so the client understands what was and was not covered.
Limitations should be agreed with the client before the inspection begins, where possible. If additional limitations become apparent during the inspection (for example, a junction box is discovered inside a ceiling void that cannot be reached), add them to the EICR and explain to the client.
The EICR includes a dedicated limitations section. Each limitation should describe what could not be inspected or tested, where it is located, and why it was not possible. An FI (Further Investigation) code may be used where the limitation means a potential defect could not be confirmed or ruled out.
The EICR records every defect and observation using the standard classification codes from BS 7671:
An immediate risk of injury. The inspector must make the installation safe before leaving — for example, by isolating a dangerous circuit. Examples: exposed live conductors, missing enclosure covers, arcing connections.
A defect that could become dangerous and requires remedial action. Examples: no RCD protection on socket circuits, Zs values exceeding maximum permitted, missing bonding conductors.
The installation does not meet the current edition of BS 7671 but is not dangerous. Advisory only — no mandatory remedial action. Examples: no supplementary bonding in a bathroom (where main bonding and RCD protection are adequate), lack of SPD protection (now recommended by Amendment 2).
The inspector could not fully assess this item. Further investigation is needed. Examples: insulation resistance marginally low but reason unclear, suspected damage to concealed cable, unusual test result requiring specialist investigation.
An EICR is classified as Unsatisfactory if any C1, C2, or FI codes are recorded. Only C3 codes alone do not make the report Unsatisfactory. See the observation codes guide for detailed examples and guidance on choosing between C2 and C3.
Describe a defect in plain English — 'no RCD on socket circuit in bathroom' — and Elec-Mate's AI returns the correct observation code with the matching…
Try it free for 7 daysA periodic inspection can be time-consuming if the workflow is not organised. Here is how Elec-Mate helps you complete EICRs faster without cutting corners:
Photograph the consumer unit. Elec-Mate reads MCB/RCBO ratings, circuit references, and board details from the image. The schedule of test results pre-fills with circuit descriptions and protective device ratings.
Speak your readings as you take them. "Ring 1, R1+R2 0.32, IR 200 megohms, Zs 0.89, RCD 18 milliseconds." The schedule fills in while your hands stay on the test leads. No putting instruments down to type.
Describe any defect in plain English. The AI returns the correct observation code (C1, C2, C3, or FI) with the matching BS 7671 regulation number. Automatically compares test results against maximum values and flags failures.
Every C1, C2, and FI observation feeds into the remedial works estimator. It prices each fix — materials, labour, margin — and generates a professional quote. Hand the client the EICR and the remedial quote in the same visit.
The completed EICR exports as a professional PDF. Send it to the client by email or WhatsApp before you leave site. No going home to type up the report. No desk time. No chasing.
AI board scanner, voice test entry, automatic defect coding, and remedial quoting — all in one app.
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