Meta Title: What is IR35? Guide for Electrical & Panel Contractors | Panelwire
Meta Description: Confused by IR35? Learn how off-payroll working rules affect electrical contractors, panel builders, and engineering firms, with tips to stay compliant.
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Whether you are an independent controls engineer wiring custom distribution boards, a freelance PLC programmer commissioning an automotive plant, or an engineering firm managing a temporary influx of workshop build capacity, IR35 directly governs how payments, tax, and employment status must be handled.
Introduced to tackle perceived “disguised employment”, the UK’s off-payroll working rules have reshaped how technical and trades contractors operate. Misclassifying an assignment can result in substantial financial penalties, clawbacks for unpaid Pay As You Earn (PAYE) Income Tax and National Insurance Contributions (NICs), and significant administrative headaches.
This guide provides a comprehensive breakdown of what IR35 is, how status determinations work in technical engineering and panel-building environments, the key tests HMRC uses, and how contractors and clients can protect their working arrangements.
1. What is IR35?
IR35 refers to the UK tax legislation set out in the Finance Act 2000 (and updated under Chapter 10 of the Income Tax (Earnings and Pensions) Act 2003). Its primary purpose is to ensure that contractors working through an intermediary—most commonly a Personal Service Company (PSC) or limited company—pay broadly the same tax and National Insurance as direct employees if their actual working relationship resembles traditional employment.
When an individual operates via a PSC, they have historically taken income as a mix of salary and dividends, reducing Employer and Employee Class 1 NIC liabilities. HMRC introduced IR35 to prevent workers from leaving permanent jobs on a Friday and returning to the exact same desk on a Monday as an “independent company”, claiming corporate tax efficiencies while operating with zero commercial risk or autonomy.
2. Inside IR35 vs Outside IR35: What Is the Difference?
Your assignment status determines how you invoice and how money flows into your bank account:
| Feature | Outside IR35 (Genuine B2B) | Inside IR35 (Deemed Employment) |
| Tax Treatment | Gross invoice paid directly to PSC; contractor manages Corporation Tax, salary, and dividends. | Treated as employment income; tax and Employee NICs deducted before payment via fee-payer PAYE. |
| National Insurance | PSC manages employer/employee contributions where applicable. | Employer NICs and Apprenticeship Levy apply to the fee payer/umbrella. |
| Employment Rights | No statutory employment rights (holiday pay, sick pay, redundancy, pension auto-enrolment). | No statutory employment rights from the end client, despite paying employee-level taxes (“zero-rights employment”). |
| Control & Direction | High degree of autonomy over how, when, and where the agreed deliverable is completed. | Supervised, directed, or controlled regarding working hours, methods, and prioritisation. |
| Equipment & Materials | Supplies own core specialist tools, testing equipment, and insurance. | Provided with tools, PPE, benches, and workshop infrastructure by the client. |
Inside IR35
If an assignment is deemed Inside IR35, HMRC views the relationship as one of employment for tax purposes. The fee-payer (which could be the end client or a recruitment agency) is legally required to deduct Income Tax and Employee NICs at source via PAYE before paying the net invoice amount to your PSC or umbrella company.
Outside IR35
If an assignment is assessed as Outside IR35, your business is operating as a genuine B2B service provider. Your limited company invoices the client or agency for the agreed project milestones or day rates, receives the full gross amount (plus VAT if VAT-registered), and distributes profit through legitimate commercial channels.
3. The 2017 and 2021 Reforms: Who Decides Your Status?
Historically, the contractor was responsible for determining their own IR35 status and paying any resulting tax liabilities. However, major reforms fundamentally shifted this burden:
- Public Sector (April 2017): Public sector organisations became responsible for determining the IR35 status of their off-payroll workers.
- Private Sector (April 2021): The rules were extended to all medium and large private sector businesses across the UK.
The Small Company Exemption
If the end client qualifies as a small business under the Companies Act 2006, the original rules still apply: the contractor’s PSC remains responsible for assessing its own status. A business is classified as small if it meets at least two of the following criteria:
- Annual turnover of no more than £10.2 million
- Balance sheet total of no more than £5.1 million
- No more than 50 employees
If your end client is medium or large, they must assess your assignment, issue a formal Status Determination Statement (SDS) detailing their reasoning, and demonstrate “reasonable care” in reaching that decision.
4. Key Factors Determining IR35 Status on the Workshop Floor
Contract wording alone does not determine your status. HMRC inspects the actual working reality of your day-to-day engagement. In electrical contracting and control panel manufacturing, three core pillars carry the most weight:
┌────────────────────────────────────────┐
│ IR35 STATUS PILLARS │
└───────────────────┬────────────────────┘
┌───────────────────────────┼───────────────────────────┐
▼ ▼ ▼
┌───────────────────┐ ┌───────────────────┐ ┌───────────────────┐
│ Right of │ │ Control & │ │ Mutuality of │
│ Substitution │ │ Direction │ │ Obligation (MOO) │
└───────────────────┘ └───────────────────┘ └───────────────────┘
1. Personal Service & Right of Substitution
Can your business provide a qualified substitute engineer to carry out the build, wiring, or commissioning if you are unavailable?
- Outside IR35 Indicator: Your contract contains an unfettered (or reasonably fettered) right of substitution, and the client agrees that as long as the replacement holds the necessary qualifications (such as 18th Edition BS 7671 or relevant panel-building competencies), they will accept them.
- Inside IR35 Indicator: The client insists that only you can perform the work because they hired your personal skills rather than purchasing a service deliverable from your company.
2. Control and Direction
How much oversight does the client exercise over your day-to-day tasks?
- Outside IR35 Indicator: You are engaged to deliver a defined scope of work—such as wiring four multi-bay motor control centres (MCCs) according to BS EN 60204-1 schematics. How you sequence the harness routing, ferrule terminations, and trunking layout is left to your professional expertise.
- Inside IR35 Indicator: The workshop manager dictates your specific break times, moves you between unrelated odd jobs on demand, micromanages your assembly technique, or subjects you to internal staff appraisal mechanisms.
3. Mutuality of Obligation (MOO)
Is there an ongoing obligation to provide and accept work?
- Outside IR35 Indicator: You are hired for a specific milestone, batch, or commissioning phase. Once completed, the contract terminates. The client is not obliged to offer more work, and you are not obliged to accept it.
- Inside IR35 Indicator: When panel builds slow down, the client keeps paying your standard day rate to sweep the workshop or complete general maintenance tasks, creating an ongoing employer-employee dynamic.
Shop-Floor Compliance Tip: Maintain documented deliverables. Always work to a defined Scope of Work (SOW) referencing specific drawings, panel numbers, or commissioning schedules, rather than open-ended time-and-materials timecards that describe generic “workshop support”.
5. Practical Steps for Contractors and Clients to Maintain Compliance
┌─────────────────────────────────────────────────────────────────────────────┐
│ OUTSIDE IR35 COMPLIANCE ROADMAP │
├─────────────────────────────────────────────────────────────────────────────┤
│ 1. Defined SOW ──► Clear start/end dates, milestone-based scope. │
│ 2. Tool Independence ──► Provide own calibrated crimpers, multimeters, PPE. │
│ 3. Commercial Risk ──► Rectify snagging/wiring errors on own time. │
│ 4. Independent B2B ──► Maintain professional indemnity & public liability.│
└─────────────────────────────────────────────────────────────────────────────┘
- Invest in Independent Tools and Calibration: Genuine subcontractors bring their own specialist equipment. While large heavy machinery (such as overhead cranes or CNC busbar benders) is naturally client-owned, bringing your own calibrated wire strippers, ratcheting ferrule crimpers, torque screwdrivers, and insulation resistance testers strengthens your commercial independence.
- Carry Commercial Risk: An independent business must rectify defective work at its own expense. If a wiring fault or incorrect cable rating is identified during factory acceptance testing (FAT) due to your installation error, your company should correct the defect on its own time without billing additional hours.
- Establish Business Infrastructure: Maintain active Public Liability and Professional Indemnity insurance, operate a dedicated business website and corporate email, and invoice on formal company letterheads.
- Avoid Employment Integration: Do not accept internal staff perks, company uniform badges, parking spaces marked for permanent employees, or access to employee-only internal HR systems.
Frequently Asked Questions (FAQ)
What happens if HMRC investigates and finds an assignment is Inside IR35?
If an assignment was incorrectly operated outside IR35, HMRC will seek back-taxes for PAYE Income Tax, Employer and Employee National Insurance Contributions, interest on late payments, and potential penalties ranging from 0% to 100% of the owed tax depending on whether the error was deemed careless or deliberate. For medium and large clients, the liability primarily sits with the fee-payer unless the contractor provided fraudulent information.
Can an electrical contractor use HMRC’s CEST tool?
Yes. HMRC provides the Check Employment Status for Tax (CEST) tool online. While HMRC states it will stand by CEST determinations provided the information entered is accurate, critics frequently note that the tool fails to adequately account for Mutuality of Obligation (MOO). Many contractors and end clients prefer independent, insurance-backed third-party contract reviews.
Does working on-site automatically place me inside IR35?
No. Physical location does not dictate IR35. Panel assembly, machine wiring, and plant commissioning inherently require physical presence at the enclosure or machine. As long as your presence is dictated by the physical nature of the equipment and not by direct employment supervision, on-site working remains compatible with an Outside IR35 determination.
Can I still work through an umbrella company if an assignment is Inside IR35?
Yes. Many contractors engaged on Inside IR35 assignments choose to work through an accredited FCSA or Professional Passport compliant umbrella company. The umbrella acts as your employer for payroll purposes, processing full PAYE and NIC deductions from the fee paid by the recruitment agency or client.
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