IR35 for UK Trade Contractors — Does It Apply to Your Trade Business in 2026?

If you run a trade business through a limited company — whether you're a sole contractor or have a small team — you've probably heard of IR35. Maybe a site manager mentioned it, or your accountant flagged it, or you've seen warnings about HMRC crackdowns. The rules are confusing, the jargon is dense, and getting it wrong is expensive.

This guide cuts through the noise. We'll explain exactly what IR35 is, when it applies to trade contractors in 2026, how it interacts with CIS, and what you can do to protect your position. As always, speak to a qualified accountant for advice specific to your situation.

What is IR35?

IR35 — formally the off-payroll working rules — was introduced to catch "disguised employees": people who work like an employee for a client but operate through a limited company to pay less tax. The name comes from Inland Revenue press release 35, published back in 1999.

The core logic is this: if you would be an employee of your client if you were working for them directly, HMRC says your limited company income should be treated as salary for tax purposes. That means income tax and National Insurance Contributions (NICs) apply at employment rates — significantly higher than the combination of a modest salary plus dividends that most Ltd company directors use.

IR35 doesn't mean you can't work through a Ltd company. It means that when IR35 applies to a specific engagement, the tax treatment of that engagement changes. You can still have a Ltd company, still have other clients, and still benefit from Ltd company efficiencies in other areas of your business.

When does IR35 apply to trade contractors?

The off-payroll working rules (Chapter 10, ITEPA 2003 — the legislation behind IR35) apply when a worker provides services to a client through an intermediary (typically a personal service company or Ltd company). Whether IR35 applies to a specific engagement depends on two things: the nature of the client, and the employment status of the worker in that engagement.

The client size rule

The rules work differently depending on how big your client is:

• Medium or large private sector clients and all public sector bodies: The client (or the agency in the chain) is responsible for determining your employment status and deducting tax if you're inside IR35. This has applied to public sector work since 2017 and to medium/large private sector since April 2021.
• Small private sector clients: If the client qualifies as a small company — meeting at least two of: 50 or fewer employees, £10.2 million or less in turnover, £5.1 million or less on the balance sheet — responsibility to determine status sits with the worker's own company. You assess your own IR35 status for each engagement.

For most domestic trade work — homeowners commissioning bathroom refits, extensions, boiler replacements, electrical rewires — the client is a private individual. Private individuals are not companies at all, so the small company exception applies by default. Domestic work for homeowners carries very low IR35 risk for this reason alone.

The risk is higher when you're contracted to work for large housebuilders, main contractors, local councils, housing associations, NHS trusts, or large commercial property managers. These are medium or large entities and the off-payroll rules apply in full.

The employment status tests: what HMRC looks at

Determining whether IR35 applies to a specific engagement involves assessing the real nature of the working relationship. HMRC looks at a set of employment status factors. None is individually decisive — it's the overall picture that matters. Here are the key ones for trade contractors:

1. Substitution

Can you send a suitably qualified substitute to do the work instead of you? A genuine, unfettered right of substitution is one of the strongest indicators that you are outside IR35. If the client is paying for "a qualified electrician to complete this first fix" and doesn't care specifically whether it's you or a substitute you send, that points to self-employment.

The substitution right must be genuine. A clause in a contract that says you can substitute but in practice the client would never allow it carries little weight. HMRC looks at what actually happens, not just what the contract says.

2. Control

Does the client control how, when, and where you work — or do they simply specify the outcome they want? An employee is told when to turn up, which methods to use, and how to spend their working day. A genuine contractor agrees to deliver a defined result and retains discretion over the method and scheduling.

For trade contractors, this can be nuanced. Site safety rules (PPE, induction, site hours) don't constitute employment-level control — they're universal site requirements. But if the client is telling you exactly what sequence to work in, requiring you to clock in and out, and directing your movements throughout the day in the same way they direct their employed workforce, that tilts toward employed status.

3. Mutuality of Obligation (MOO)

Is there an ongoing obligation for the client to offer you work, and an obligation for you to accept it? Employment relationships typically involve this mutual expectation. A contractor relationship should have clear boundaries: you agree to do a specific job, complete it, and the engagement ends. Neither party is obligated to continue.

If you've been working on the same site for the same main contractor for three years and you both assume the work will continue indefinitely, MOO is a concern. If you're brought in for a specific project with a clear end date, it's much less of an issue.

4. Financial risk

Do you quote fixed prices and carry the financial risk if something goes wrong? A genuine contractor prices a job, and if it takes longer or materials cost more than expected, they bear that cost. Employees are paid for their time regardless of outcomes.

If you price bathroom fits at a fixed rate, stand behind your work with a guarantee, and absorb the cost of remedial work, that supports an outside-IR35 position. If you're paid a day rate for however long the client keeps you on site, with no financial exposure if the job overruns, that looks more like employment.

5. Part and parcel

Are you integrated into the client's workforce — attending their staff meetings, using their email systems, appearing on their org charts — or are you clearly a separate business operating on their premises temporarily? The more integrated you appear, the more employment-like the relationship.

IR35 and CIS: two separate systems

A common point of confusion for trade contractors is the relationship between IR35 and the Construction Industry Scheme (CIS). They are entirely separate systems designed to do different things.

CIS is a tax collection mechanism for the construction sector. Contractors deduct 20% (or 30% for unverified subcontractors) at source from payments to subcontractors and pass it to HMRC as an advance against the subcontractor's income tax liability. CIS says nothing about employment status.

IR35 determines whether a worker's Ltd company income should be treated as employment income for tax purposes.

A trade contractor can be subject to CIS deductions and outside IR35 at the same time. The fact that a contractor receives gross payments or is CIS-registered does not prove or disprove their IR35 status. Equally, being inside IR35 doesn't exempt you from CIS — you could theoretically be subject to both.

In practice, most small trade businesses working through CIS for domestic clients are outside IR35 anyway, because domestic homeowners are small clients. The overlap becomes more relevant when working for medium/large main contractors under CIS — in those cases, both systems apply and the employment status question is live.

Inside vs outside IR35: what it means financially

The financial difference between inside and outside IR35 is significant. Here's an illustrative comparison for a trade contractor billing £60,000 in a tax year (2026/27 rates, approximate figures — get personalised figures from your accountant):

Indicative figures only. Your actual liability depends on your full income, allowable expenses, pension contributions, and other factors. Speak to a qualified accountant.

When a client determines you are inside IR35, they apply a "deemed payment" calculation. They deduct income tax and NICs from your invoice (after a small adjustment for employer NICs), and your company receives the net amount. You do not get the tax back — it has been paid. You can still pay yourself a salary from your company up to the deemed salary amount without further income tax.

How to protect your outside-IR35 position

If you're working for medium/large clients and believe you are outside IR35, there are practical steps to document and defend that position:

Get your contracts reviewed

Your written contract should reflect the genuine nature of the relationship: project-based scope, right of substitution, no obligation to offer or accept further work, payment by deliverable rather than by time. An employment status specialist or IR35 contract reviewer typically charges £200–£500 for a review. For an engagement worth tens of thousands, that's a sensible investment.

Use HMRC's CEST tool

HMRC's Check Employment Status for Tax (CEST) tool at gov.uk produces a status determination when you answer a set of questions about the engagement. The result is not legally binding — HMRC can still challenge your status — but completing CEST and retaining the result demonstrates reasonable care. If CEST says outside IR35, that is useful supporting evidence. HMRC has committed to stand by CEST results where the tool has been used correctly and the facts are as stated.

Make substitution genuine

If your contract includes a substitution clause, make sure it reflects reality. Have you actually substituted, or could you? Can you name a qualified individual who could step in? Document this. A clause that exists purely for IR35 purposes but would never be honoured in practice is worthless.

Invoice per project, not per day

Fixed-price project invoicing looks more like self-employment than day-rate invoicing. If you currently bill by the day, consider whether project-based pricing is commercially viable for your type of work. Many trade contractors already work this way naturally.

Work for multiple clients

A genuine business typically has more than one client. If 95% of your income comes from a single site indefinitely, the relationship starts to look like disguised employment. Working across several clients — even if one dominates — strengthens your position.

Provide your own tools and equipment

Genuine contractors typically supply their own specialist tools and equipment. If the client supplies everything you need to work, including all tools, that nudges toward employment. Carry your own kit, and make this visible in contracts where relevant.

Carry appropriate insurance

Genuine businesses hold public liability insurance and, where relevant, professional indemnity or employers' liability insurance. This is both good practice and evidence of operating as an independent business. Employees don't hold their own public liability policies.

Who needs to worry most in 2026?

Not every trade contractor faces meaningful IR35 risk. Here is a practical breakdown:

Higher risk: long-term site work for large clients

• Trade contractors working 6+ months continuously on-site for a large housebuilder, main contractor, or developer
• Contractors on-site at public sector projects — NHS builds, local authority housing, schools, highways
• Workers who receive their work schedule from the client, use client tools, and have a de facto permanent desk or van bay on a client site
• Contractors where the same client accounts for most or all of their income, year after year

Lower risk: domestic and small-client trade work

• Electricians, plumbers, roofers, plasterers, and other tradespeople working primarily for domestic homeowners
• Contractors taking short jobs — days or a few weeks — across multiple clients
• Tradespeople who quote fixed prices, carry their own kit, and move between jobs independently
• Businesses where no single client dominates revenue

If you fit the lower-risk profile, IR35 is unlikely to be an urgent concern. If you fit the higher-risk profile, getting advice now is significantly cheaper than a retrospective HMRC inquiry.

Practical steps to take now

1. Review your current client list. For any engagement lasting 2+ months with a single medium or large client, assess whether IR35 could apply. If in doubt, get a contract review.
2. Document your substitution right. If your contract includes a substitution clause, ensure it is genuine. If you don't have a written contract with long-term clients, get one drafted. This protects both parties.
3. Review how you invoice. If you are billing a single large client by the day for an open-ended engagement, consider moving to project-based billing with defined scope. This is better practice financially as well as from an IR35 perspective.
4. Use CEST. Run through HMRC's tool for any engagement you are unsure about. Retain a PDF of the result.
5. Talk to your accountant. IR35 is genuinely complex and the consequences of getting it wrong are significant. A specialist accountant who works with contractors can assess your specific situation, review your contracts, and advise on structuring your business correctly.
6. Don't let a client pressure you into a status determination. If a large client issues a Status Determination Statement (SDS) saying you are inside IR35 and you disagree, you have the right to challenge it through the client's disagreement process. Get professional advice before accepting a determination you believe is wrong.

A note on the rules in 2026

The off-payroll working rules have been in their current form since April 2021 and there have been no significant legislative changes since then. HMRC continues to actively enforce the rules, particularly in construction and engineering, and has published several compliance campaigns targeting the sector. The thresholds for small company exemption (£10.2m turnover, £5.1m balance sheet, 50 employees) remain unchanged as of 2026. Always check the latest HMRC guidance at gov.uk as rules can change, and get professional advice before any significant business decision.