What is IR35 and does it affect freelancers?

IR35 is UK tax legislation (formally called the 'off-payroll working rules') designed to identify contractors and freelancers who work like employees but operate through their own company or as a sole trader to pay less tax. If HMRC determines your working arrangement is 'inside IR35', you must pay roughly the same tax as an employee — including Income Tax and National Insurance at employed rates. If you're 'outside IR35', you can take advantage of the more tax-efficient arrangements available to genuinely self-employed people.

Who decides whether a freelancer is inside or outside IR35?

Since April 2021, the responsibility for determining IR35 status shifted to the end client (the business hiring you) for medium and large private sector companies. Small companies in the private sector, and all public sector clients, must also make this determination. If you work for a small private company (under 2 of: £10.2m turnover, £5.1m balance sheet, 50 employees), the responsibility remains with you as the contractor. For sole traders working directly with clients (not through a limited company), IR35 technically doesn't apply in the same way, but the underlying employment status rules still do.

Guide · February 2026 · 12 min read

IR35 for Freelancers UK: The Complete Guide (2026)

Q: What are the three main tests for IR35?

The three key tests HMRC uses are: 1) Personal service — Can you send a substitute to do the work in your place? If yes, this points outside IR35. 2) Control — Does the client control how, when, and where you work? If yes, this points inside IR35. 3) Mutuality of obligation — Is the client obliged to offer you work, and are you obliged to accept it? If yes, this points inside IR35. No single factor is decisive; HMRC considers the overall picture. Other factors include financial risk, provision of equipment, and whether you're 'part and parcel' of the client's organisation.

IR35 is the single most important tax rule for UK freelancers and contractors. Get it wrong and you could owe HMRC thousands in back-tax. Get it right and you keep more of what you earn. Here's everything you need to know — in plain English.

What Is IR35?

IR35 is tax legislation — officially called the "off-payroll working rules" — that targets people who work like employees but operate through their own limited company (or sometimes as sole traders) to pay less tax.

The name "IR35" comes from the Inland Revenue press release that introduced it back in 1999. It stuck.

The basic idea: if you'd be an employee were it not for the intermediary (your limited company), you should pay roughly the same tax as an employee.

💡 Why it matters: The tax difference between being inside and outside IR35 can be £10,000-£25,000+ per year on typical contractor earnings. That's not a rounding error — it's your livelihood.

Inside vs Outside IR35 — What It Means for Your Tax

Outside IR35 means HMRC accepts you're genuinely self-employed. You can:

Pay yourself a small salary + dividends (much more tax-efficient)
Claim business expenses against corporation tax
Pay Corporation Tax at 19-25% on profits
Take advantage of the dividend allowance

Inside IR35 means HMRC considers you a "deemed employee". You must:

Pay Income Tax at employed rates on your contract income
Pay employee National Insurance contributions
Your client (or agency) pays employer's NI too
You get a 5% allowance for business costs (small consolation)

The Three Key Tests HMRC Uses

There's no single IR35 test. HMRC looks at the overall picture, but three factors carry the most weight:

1. Personal Service (Substitution)

The question: Can you send someone else to do the work in your place?

If you have a genuine, contractual right to send a qualified substitute — and you've actually done it, or could realistically do it — this is the strongest indicator you're outside IR35.

If the client expects you personally and wouldn't accept anyone else, that looks like employment.

            Reality check: Most freelancers can't genuinely substitute. Your personal expertise is why you were hired. But having the contractual right — even if rarely exercised — helps. And if your contract explicitly says you can sub, make sure the client would actually accept it.
        

2. Control

The question: Does the client control how, when, and where you do the work?

Outside IR35: You decide your own methods, hours, and location. The client specifies what they want delivered, not how.
Inside IR35: The client dictates your working hours, requires you to work on-site, tells you how to approach the work, and manages you like a team member.

3. Mutuality of Obligation (MOO)

The question: Is the client obliged to offer you work, and are you obliged to accept it?

Outside IR35: You complete defined projects/deliverables. Between projects, there's no obligation on either side.
Inside IR35: You're expected to be available during set hours. The client gives you ongoing work. You can't easily refuse tasks.

Who Decides Your IR35 Status?

This changed significantly in April 2021. Here's the current position:

Client Type	Who Decides IR35 Status
Large/medium private company	The end client
Small private company*	You (the contractor)
Public sector	The end client

*Small company = meets 2 of 3: turnover under £10.2m, balance sheet under £5.1m, fewer than 50 employees.

When the client decides, they must give you a Status Determination Statement (SDS) explaining their decision. If you disagree, you have the right to dispute it — and the client must respond within 45 days.

⚠️ Watch out: Some clients use "blanket assessments" — declaring all contractors inside IR35 to avoid risk. This is against HMRC guidance but happens frequently. If your client does this, push back with evidence of your genuine self-employment.

Does IR35 Apply to Sole Traders?

Technically, IR35 specifically targets intermediaries (mainly limited companies and partnerships). If you work as a sole trader, IR35 doesn't apply in the same way.

However — and this is important — HMRC can still challenge your employment status under general employment law. The same three tests (substitution, control, MOO) still matter. If HMRC decides you're actually an employee of your client, you'd owe the same tax.

The practical difference: for sole traders, HMRC pursues this under Section 49 ITEPA 2003 rather than IR35. The tax outcome is similar.

The Tax Difference: Inside vs Outside (Real Numbers)

Here's what IR35 status means in pounds and pence on a £75,000 contract:

Item	Outside IR35	Inside IR35
Gross Contract	£75,000	£75,000
Corporation Tax / Employer's NI	~£3,400 CT	~£8,400 Er's NI*
Salary + Dividends / Deemed Pay	£12,570 salary + £59,000 dividends	~£62,400 deemed pay
Income Tax	~£5,900	~£12,400
Employee's NI	~£180	~£4,600
Total Tax	~£12,300	~£25,400
Take Home	~£62,700	~£49,600

*Employer's NI deducted from contract value before deemed pay. Figures approximate for 2025/26 tax year.

            The difference: ~£13,100/year. Over a typical 3-year contract, that's nearly £40,000. This is why IR35 status matters so much.
        

7 Ways to Protect Yourself from an IR35 Investigation

1. Get Your Contract Right

Your contract is the first thing HMRC examines. Ensure it includes:

A genuine right of substitution
No control clauses (you decide how/when/where)
Defined deliverables, not ongoing services
No "mutuality of obligation" language
A clear termination clause (not notice period like an employee)

Our Contract Template Pack includes IR35-friendly clauses.

2. Match Your Working Practices to Your Contract

A perfect contract is worthless if you actually work like an employee. HMRC looks at reality, not just paperwork.

3. Work for Multiple Clients

Having more than one client at a time is strong evidence of genuine self-employment. Even occasional side projects help.

4. Use Your Own Equipment

Bringing your own laptop, software licenses, and tools demonstrates you're running a real business, not just borrowing your client's desk.

5. Don't Integrate into the Client's Team

Avoid: using the client's email address, attending staff social events, being included in org charts, having a permanent desk, and participating in performance reviews.

6. Take Financial Risk

Employees don't risk losing money if a project goes wrong. If you have fixed-price contracts, offer warranties on your work, or cover your own costs for mistakes — document it.

7. Get IR35 Insurance

IR35 tax investigation insurance (from providers like Qdos, Kingsbridge, or IR35 Shield) typically costs £100-300/year and covers legal defence costs if HMRC investigates. Some also provide status assessments.

HMRC's CEST Tool — Should You Use It?

HMRC's Check Employment Status for Tax (CEST) tool is free and gives you HMRC's view of your IR35 status. However:

Pros: It's free, and HMRC will stand by the result (if you answer honestly). Good for a quick check.
Cons: It often gives "indeterminate" results. It doesn't consider all relevant factors. The questions can be confusing. And some tax specialists argue it's biased toward "inside IR35" results.

Use it as a starting point, but consider a professional IR35 review for high-value contracts. Companies like Qdos, IR35 Shield, and Bauer & Cottrell offer detailed assessments for £75-300.

What Happens If HMRC Says You're Inside IR35?

HMRC opens an investigation — They'll examine your contracts, working practices, and evidence
You can dispute their determination — Provide evidence of genuine self-employment
If found inside IR35: You'll owe the difference in tax + NI for all affected tax years (up to 6 years back, or 20 years if deliberate evasion)
Penalties — 0-100% of the tax owed, depending on whether HMRC considers it careless or deliberate
Interest — Charged on late payment from the original due date

💡 Important: Since April 2021, for medium/large clients, the liability falls on the fee-payer (usually the agency or client), not you. But for small company clients where you make the determination, the liability remains with your company.

Common IR35 Mistakes Freelancers Make

Only focusing on the contract: HMRC looks at working practices first. Your contract is evidence, but reality trumps paperwork.
Working for one client for years: The longer you work exclusively for one client, the more it looks like employment.
Accepting a blanket "inside" determination without challenging it: Many clients assess everyone the same to minimise their risk. You can dispute this.
Not keeping evidence: Document everything — emails showing control (or lack of), invoices to multiple clients, proof of equipment ownership.
Ignoring IR35 because you're a sole trader: Employment status rules still apply even without a limited company.

Bulletproof Your Freelance Contracts

Our Contract Template Pack includes IR35-friendly clauses, payment protection, and scope definitions — all reviewed for UK law.

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