3.2 The Minor Electrical Installation Works Certificate (MEIWC)

The Minor Electrical Installation Works Certificate (MEIWC)

The Minor Electrical Installation Works Certificate (MEIWC) is the documentation issued for small additions or alterations to an existing electrical installation that do not require the provision of a new circuit and do not extend to a new distribution board or consumer unit.

When the MEIWC is Used

The MEIWC is appropriate for limited, self-contained modifications such as:

• Adding a socket outlet to an existing ring final circuit
• Adding a lighting point or a fan to an existing lighting circuit
• Modifying an existing circuit (for example, relocating a switch or extending a radial)
• Replacing a damaged cable section within an existing circuit

The common thread is that no new circuit is created and the work does not warrant re-energising and fully verifying the whole installation from new.

When the MEIWC is NOT Appropriate

The MEIWC must not be used for:

• A new circuit of any kind
• A new distribution board or consumer unit installation
• A consumer unit replacement
• A rewire or a major addition
• Any work that requires the whole installation to be fully re-verified and re-energised for the first time

These jobs require a full Electrical Installation Certificate (EIC) with all three parts.

The Single-Page Document

Unlike the EIC, which has three separate parts, the MEIWC is a single-page document. It combines the relevant declarations and test results onto one sheet — there is no separate schedule of test results and no separate schedule of inspections. This reflects the limited scope of the work.

The MEIWC records:

1. Description of the minor work — the location and nature of the alteration
2. Circuit details — the circuit affected and its protective device
3. Existing supply characteristics — Ze, PFC, and type of earthing at the origin (these confirm the existing installation's baseline)
4. Test results for the modified work — continuity of protective conductors (R1+R2), insulation resistance, polarity, and the Zs of the modified circuit measured at the furthest point
5. RCD operation (if an RCD or RCBO is part of the modified circuit) — tripping time at 1× and 5× rated residual current
6. Inspector's signature — declaring that the work complies with BS 7671

What the Inspector Declares

By signing, the inspector declares that the minor works described have been designed, constructed, inspected, and tested in accordance with BS 7671:2018+A4:2026. The inspector is also responsible for verifying that the existing installation can safely support the addition — for example, that the existing protective device and earthing arrangements remain adequate after the modification. This means the inspector must check that the existing Zs at the modified circuit's furthest point still permits the required disconnection time, and that adding the load does not overload the circuit's rated capacity.

What the MEIWC Does NOT Record

Because the MEIWC covers only the modified portion of one circuit, it does not require a full re-test of the entire installation. The existing supply characteristics (Ze, PFC, earthing type) are referenced from the original EIC or the most recent EICR — they are not re-measured in full unless there is reason to believe they have changed. This is a key reason why the MEIWC is a single page: the scope of verification is deliberately narrow.

Borderline Cases

Some jobs sit on the boundary between MEIWC and EIC. The deciding test is always whether a new circuit is created:

• Extending a ring final circuit with an additional socket — MEIWC (same circuit, no new circuit).
• Adding a spur from a consumer unit to a new cooker — EIC (new circuit, even though it is a single load).
• Replacing a consumer unit — EIC (the distribution board has changed; the whole installation must be re-verified).
• Adding a light and fan to an existing lighting circuit — MEIWC (same circuit, no new circuit).

When in doubt, the safer choice is the full EIC. Issuing a MEIWC for work that actually creates a new circuit is a documentation error that undermines the compliance record.

EIC vs MEIWC — Key Contrast

Common Exam Trap

A frequent exam scenario asks which certificate to issue for "adding a socket to an existing ring final circuit." The correct answer is the MEIWC, because no new circuit is created. However, if the question states the work involves "a new circuit supplying a cooker," the answer is the EIC, regardless of how small the load is — a new circuit always requires an EIC, never a MEIWC.