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IR35 for Consultants: How to Stay Outside the Rules

IR35 is one of the biggest tax risks facing consultants who operate through a limited company. Get it wrong and HMRC can treat your income as employment income, wiping out the tax advantages of trading through your own company. This article explains what IR35 actually means for consultants, how the rules work in practice, and the concrete steps you can take to stay outside them.

What is IR35 and why does it matter for consultants?

IR35 is a set of off-payroll working rules introduced by HMRC to tackle what it calls disguised employment. The basic idea is this: if you work through a limited company but your day-to-day reality looks like employment — one client, set hours, a line manager telling you what to do — HMRC believes you should pay roughly the same tax as an employee.

For consultants, the financial stakes are significant. Operating outside IR35 through a limited company allows you to take a low salary and draw dividends, which are taxed at lower rates than employment income. In 2026/27, dividends above the £500 allowance are taxed at 10.75% for basic rate taxpayers and 35.75% for higher rate taxpayers. That is substantially less than the 20% or 40% income tax plus National Insurance that applies to employment income.

If HMRC decides you fall inside IR35, it effectively treats the money your company receives as a salary. You pay income tax and National Insurance on it, and you lose most of the tax efficiency that made trading through a limited company worthwhile in the first place.

How IR35 status is decided

IR35 status is not a simple checklist. HMRC looks at the overall picture of your working relationship with a client and asks one central question: if you stripped away the limited company, would this person be an employee?

To answer that question, HMRC looks at your contract and, more importantly, how you actually work. These two things must match. A contract that says you can send a substitute but you have worked exclusively for one client for three years, in their office, under their supervision, will not protect you.

Employment tribunals and tax cases have developed several tests over the years to help make this determination. Three of them carry the most weight.

The three tests that matter most

1. Substitution

Can you send someone else to do the work in your place? This is called the right of substitution, and it is one of the strongest indicators of genuine self-employment. If a client has hired you personally and would reject anyone you tried to send in your place, that looks like employment. If your contract allows substitution and you could genuinely exercise that right, it points towards being outside IR35.

The substitution must be real. A clause buried in a contract that has never been exercised and would never be accepted in practice will not fool HMRC.

2. Control

Who decides how, when, and where you work? Employees are told what to do and how to do it. Genuinely self-employed consultants are engaged for a result — the client cares about the outcome, not the method.

If a client sets your hours, requires you to work on-site every day, tells you exactly how to do your work, and manages you like a staff member, that is a control indicator pointing inside IR35. If you set your own schedule, choose your methods, and deliver an agreed output, that points the other way.

3. Mutuality of obligation

Mutuality of obligation means: is the client obliged to offer you work, and are you obliged to accept it? Employees have this — your employer offers shifts or projects and you are expected to turn up. Consultants should not. Each project or contract should be a discrete engagement with no expectation of ongoing work on either side.

If you and a client have worked together continuously for years with no formal break and no renegotiation, that ongoing expectation of work and pay looks like employment.

Public sector vs private sector: who decides your status?

This is where the rules changed significantly in 2017 and again in 2021, and many consultants are still unclear on how it works.

Public sector engagements

Since April 2017, public sector organisations — NHS bodies, local councils, government departments — are responsible for deciding whether IR35 applies to contractors they engage. They must issue a Status Determination Statement (SDS) telling you whether they regard you as inside or outside IR35. If they decide you are inside, they deduct income tax and National Insurance before paying your company.

Private sector engagements (medium and large businesses)

Since April 2021, medium and large private sector businesses have also been responsible for making IR35 determinations for the contractors they engage. The same SDS process applies. If the end client decides you are inside IR35, the fee-payer in the supply chain — often a recruitment agency — must operate PAYE.

Small private sector clients

If your client is a small company — broadly, one that meets two of the three criteria: turnover under £10.2 million, fewer than 50 employees, balance sheet under £5.1 million — the responsibility for determining IR35 status stays with you and your limited company. This means you have more control over your position, but also more responsibility for getting it right.

Many freelancers and consultants work primarily with small clients, which is why understanding the rules yourself remains so important.

Practical steps to stay outside IR35

Staying outside IR35 is not just about what your contract says. It is about how you genuinely operate. Here are the most effective things you can do.

  • Work with multiple clients. Having several clients at once is one of the clearest signals of genuine self-employment. It is difficult for HMRC to argue you are a disguised employee of one company when you are simultaneously delivering projects for three others.
  • Take financial risk. Genuine businesses bear financial risk — they invest in equipment, carry professional indemnity insurance, quote for fixed-price projects, and can lose money on a contract. If you absorb no risk at all, that looks like employment.
  • Have a proper business presence. A professional website, business email, your own equipment, your own software licences, and a separate business bank account all support the picture of a genuine independent business.
  • Avoid being integrated into the client’s organisation. Do not appear on the client’s internal directory. Do not use a client email address. Do not attend staff events as a member of the team. The more you look like part of the furniture, the more HMRC will argue you are.
  • Negotiate your own terms. Employees accept the terms they are offered. Consultants negotiate their rate, scope, deliverables, and timelines. Document those negotiations.
  • Use a written contract for every engagement. Always. Even with clients you know well.

Getting your contract right

Your contract is the starting point for any IR35 assessment. It needs to reflect genuine self-employment — not just use the right words.

Have every new contract reviewed by an IR35 specialist before you sign it. This is not expensive relative to the potential tax liability if HMRC comes knocking. A good contract will include:

  • A genuine right of substitution clause
  • Clear project-based deliverables rather than open-ended duties
  • No guaranteed minimum hours or pay
  • Termination provisions that reflect a commercial relationship, not employment
  • Clear statements about who provides equipment and tools
  • Confirmation that you are responsible for your own tax affairs

Read the contract carefully yourself. If it says you must work at the client’s site Monday to Friday from 9am to 5pm and report to a named manager, no amount of clever drafting elsewhere will save you.

HMRC’s Check Employment Status for Tax (CEST) tool is available online and gives an indication of status. It is not perfect — it has been criticised for omitting mutuality of obligation — but it is the tool HMRC itself uses, so running your contract through it is worthwhile.

Working practices: the real danger zone

Working practices are what actually happens on the ground, and HMRC will look at these hard during any investigation. Your contract can say all the right things, but if your real-world behaviour tells a different story, the contract will not protect you.

Ask yourself these questions honestly:

  • Do I work exclusively for this one client?
  • Have I been with this client for more than two years without a meaningful break?
  • Do I attend their site daily and follow their working hours?
  • Does my line manager set my tasks and review my work?
  • Do I use their equipment, their systems, their email address?
  • Would they object if I sent a substitute?
  • Am I paid a regular fixed amount regardless of output?

If you answered yes to several of those, your working practices are pointing inside IR35 regardless of what your contract says. That is the time to have a serious conversation with your accountant and consider whether the engagement needs restructuring.

Good bookkeeping also matters here. Keeping clear records of invoices, project deliverables, correspondence, and payments creates an audit trail that demonstrates you operate as a genuine business.

What happens if HMRC decides you are inside IR35?

If HMRC opens an IR35 investigation and decides your engagements should have been taxed as employment, the consequences are serious.

HMRC will calculate a deemed payment — essentially treating the income your company received as gross employment income — and work out how much income tax and National Insurance should have been paid. You will owe the difference, plus interest, plus potentially a penalty if HMRC believes you were careless or deliberate.

HMRC can investigate up to four years back for innocent errors, six years for careless errors, and up to 20 years for deliberate behaviour. The potential liability can be substantial.

Your limited company’s corporation tax position also changes. You cannot claim the same deductions because the income is recharacterised. And if you have already drawn dividends rather than salary, you may have paid less National Insurance than you should have.

IR35 insurance — sometimes called tax investigation insurance — is worth considering. It covers professional fees if HMRC investigates. It does not cover the actual tax owed if you are found to be inside IR35, but it does cover the cost of defending your position.

If you receive a Status Determination Statement from a client that you disagree with, you have the right to challenge it through the client’s disagreement process. Get proper advice before doing so.

Keeping your annual accounts accurate and your company records in good order makes any investigation significantly easier to manage. If your accountant is already across your finances, responding to HMRC enquiries is faster and less stressful.

Consultants who are genuinely outside IR35 have nothing to fear from HMRC, provided they can demonstrate it. The key is to structure your engagements correctly from the outset, keep clear records, and take professional advice when a new contract raises questions.

Frequently asked questions

Can I be outside IR35 if I only have one client?

Yes, but it is harder to demonstrate. Having one client does not automatically put you inside IR35 — the three main tests still apply. However, a long-running single-client arrangement with no substitution rights, high control, and daily on-site working will struggle to pass those tests. Multiple clients make the case much easier.

Does working from home help with IR35?

It can, because it reduces the integration and control indicators associated with employment. If you work from your own office, use your own equipment, and set your own hours, that supports the case for genuine self-employment. But it is not decisive on its own — the full picture of your working relationship still matters.

How far back can HMRC investigate IR35?

HMRC can typically go back four years for innocent errors, six years for careless errors, and up to 20 years where there has been deliberate non-compliance. This is why getting your status right from the start matters far more than hoping an issue never comes up.

What is a Status Determination Statement and do I need one?

A Status Determination Statement (SDS) is a written decision from your end client setting out whether they consider your engagement to be inside or outside IR35. It is legally required from medium and large private sector clients and all public sector bodies. If you work with small private sector clients, you are responsible for your own determination — no SDS is required from them.

Does IR35 apply if I am a sole trader rather than a limited company?

IR35 specifically targets consultants operating through an intermediary, most commonly a limited company or personal service company. If you trade as a sole trader, IR35 does not apply in the same way. However, HMRC can still challenge whether you are genuinely self-employed using general employment status rules. The risk is different but it is not zero.

Should I use HMRC’s CEST tool to check my status?

CEST (Check Employment Status for Tax) is a useful starting point and HMRC will stand by its output if you answer the questions accurately and honestly. However, it does not cover every scenario and has limitations around mutuality of obligation. Use it as one input alongside a proper contract review and professional advice, not as the only answer.