Voice and visuals made with automated software, including AI.
Yes, for installing a whole electrical system, such as a full rewire. As of October 2026, HMRC treats repairs, extra sockets, burglar alarms, security CCTV and stand-alone data cabling as outside CIS, unless part of a wider building contract.
The Construction Industry Scheme (CIS) covers installing systems of lighting, power supply, heating, ventilation, air-conditioning and fire protection in a building, under section 74 of the Finance Act 2004. HMRC's CIS manual and its CIS 340 guide explain where the line falls for electrical work. This page follows those sources as checked on 17 October 2026.
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Install is in, repair is out
HMRC's manual page on building service systems draws three lines for electricians:
- Installing a system is covered. Replacing a whole system also counts as installing one, and the manual's own example is a complete electrical rewire.
- Repairing or maintaining a system is not. The manual lists rewiring a single defective circuit and replacing a burned-out ventilation fan motor as repairs.
- Extending or altering a system is not either. The manual's example is wiring additional plug sockets.
Two situations bring repairs and extensions back in. If a repair contract includes any making good to the building itself, every payment under that contract is covered. And if a building is extended with an extra floor or a side extension, any wiring extended under the same contract is caught, because the contract is for building work.
Lighting outside a building can be covered too. The manual's example is running power lines to lights some distance from the walls: power lines are works forming part of the land, which section 74 includes.
Electrical jobs, in or out
| Job | CIS? | Why |
|---|---|---|
| Full rewire of a house or building | In | Replacing a system counts as installing one |
| Wiring and lighting in a new build | In | Installing a system |
| Extra sockets or a circuit on their own | Out | Extending a system |
| Fault-finding, or rewiring one bad circuit | Out | Repair |
| Wiring for an extension, under the builder's contract | In | Part of a contract to extend the building |
| Power lines to external lights | In | Works forming part of the land |
| Complete air-conditioning installation | In | Replacing parts only is out |
| Solar panels to provide electricity | In | Except a contract directly with a private householder |
| Fire alarm or detection that only sounds a warning | Out | Treated like a security warning system |
| Fire detection that also sets off sprinklers | In | A system of fire protection |
| Burglar alarm, security CCTV, public address | Out | Security systems are excluded by law |
| Door entry with only an electronic lock and voice link | Out | A security system |
| CCTV for traffic management | In | Not a security system |
| Computer or phone network on its own | Out | In only if it needs other construction work on the building |
| Inspecting, adjusting and reporting on an installation | Out | Treated like a survey |
The fire alarm rows come from HMRC's page on fire protection systems. Alarm-only systems are treated as a public safety function, like security warnings, while detection that triggers structural protection such as sprinklers is a fire protection system. CIS 340 also excludes installing or replacing telecommunication or computer wiring through existing ducting in a building.
Commissioning and testing
HMRC's manual says commissioning can go either way. If the work is no more than inspecting an installation, adjusting controls and reporting back, it is treated as a survey and is outside CIS. If the contract also requires you to put right physical faults you find, that completes the earlier work and is covered. Where the installation itself was outside CIS, commissioning it is outside too.
One contract, one answer
CIS looks at the contract, not the invoice. HMRC's manual uses an electrician as its example: a contract to rewire a building and install a burglar alarm. The rewire is covered and the alarm is not, but because both sit in one contract, every payment is covered, even if you send separate invoices. HMRC calls this a mixed contract.
What this means for you
The same electrician can be inside CIS on one job and outside it on the next. A rewire for a builder is covered; a fault call for a shop is not. What decides it is the work in each contract and who is paying you. A homeowner paying you direct is not a CIS contractor, but a builder paying you for a homeowner's job is, as the homeowner guide explains.
If a contractor takes deductions from a contract that is wholly outside the scheme, CIS 340 says contractors should make sure that does not happen, so raise it with them. Money from jobs outside CIS is still business income for your tax return. The wider list of covered work is in the guide to what work is covered by CIS.
Steps to check an electrical job
- Ask who is paying you. A private homeowner paying direct is not a CIS contractor.
- Ask whether you are installing a whole system, including a full rewire, or repairing or adding to one.
- Check the job against the table above, especially alarms, CCTV, data cabling and fire detection.
- Read the whole contract. If any part of it is covered, every payment under it is covered.
- If CIS applies, make sure the contractor can verify you, and keep each monthly payment and deduction statement.
- Record CIS and non-CIS income separately, so your deductions match your statements at the year end. The electrician expenses guide covers the costs side.
The free MTD check shows when Making Tax Digital starts for you, and the trades section has more guides on CIS.
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Questions people ask
Is a full rewire covered by CIS?
Yes. HMRC's manual says replacing a whole system, such as a complete electrical rewire, counts as installing a system, which is within CIS.
Does adding sockets come under CIS?
Not on its own. HMRC treats wiring extra sockets as extending a system, which is outside CIS, unless it is done under the same contract as building work such as an extension.
Are fire alarms covered by CIS?
Fire alarm and detection systems that only give an audible or visible warning are outside CIS. Fire detection that also sets off sprinklers or other structural fire protection is inside.
Is installing security CCTV or a burglar alarm covered by CIS?
No, the law excludes security systems, though digging or concrete posts for the cameras are covered. And if one sits in the same contract as covered work, such as a rewire, every payment under that contract is in CIS, even on separate invoices.
Is solar panel installation covered by CIS?
Yes. HMRC's manual says installing solar panels to provide electricity is within CIS, except where the contract is directly with a private householder.
Sources
- Finance Act 2004, section 74: Meaning of construction operations (legislation.gov.uk)
- CISR14090: The Scheme: construction operations: building service systems (HMRC manual)
- CISR14160: The Scheme: construction operations: fire protection systems (HMRC manual)
- CISR14290: The Scheme: construction operations: security systems (HMRC manual)
- CISR14130: The Scheme: construction operations: computer and telephone networks (HMRC manual)
- CISR14120: The Scheme: construction operations: commissioning (HMRC manual)
- CISR14030: The Scheme: construction operations: unusual contracts (HMRC manual)
- Construction Industry Scheme: a guide for contractors and subcontractors (CIS 340), Appendices A and C (GOV.UK)
This is general information to help you understand the rules. It isn't tailored to your circumstances, so check your own position before acting on it.
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All CIS guides for subcontractors
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