IR35 explained: what UK freelancers need to know in 2026

IR35 is the most misunderstood piece of tax legislation affecting UK freelancers. It was introduced to tackle 'disguised employment', people who work like employees but invoice through a limited company to pay less tax. But it catches genuine freelancers too, and the consequences can be severe.

What IR35 actually means for your pay

If your engagement is determined to fall 'inside IR35', you are taxed as if you were an employee. That means PAYE income tax, employee National Insurance, and your client pays employer National Insurance too. The net effect on your take-home pay can be a reduction of up to 25%.

What changed and what is changing

Since April 2021, medium and large private sector clients have been responsible for determining your IR35 status, not you. This shifted the risk and led many companies to issue blanket 'inside IR35' determinations to avoid liability, even when the actual working arrangement was outside.

From April 2026, new rules introduce joint and several liability, meaning end clients, agencies, and umbrella companies can all be held responsible for getting the determination wrong. This is meant to encourage more accurate assessments, but it also adds complexity.

How to stay outside IR35

HMRC looks at the reality of your working arrangement, not only what your contract says. Three tests determine your status:

• Control: do you decide how, when, and where you work? Or does the client dictate your schedule and methods?
• Substitution: could you send someone else to do the work in your place? If yes, that suggests genuine self-employment
• Mutuality of obligation: is the client obliged to offer you work, and are you obliged to accept it? If not, you are more likely outside IR35

Practical steps to protect yourself

• Use HMRC's free CEST tool as a starting point, but do not rely on it alone
• Ensure your contract reflects reality: include substitution clauses, no obligation of exclusivity, your own equipment
• Work for multiple clients simultaneously where possible; this demonstrates business independence
• Keep records of how you work: your own tools, your own schedule, project-based deliverables not hours
• If a client gives you an 'inside' determination you disagree with, you have the right to challenge it; they must respond within 45 days

The umbrella company warning

If you work through an umbrella company, be extremely cautious about schemes promising high take-home rates. Non-compliant umbrellas may be using tax avoidance arrangements that leave you personally liable for unpaid tax. If a deal looks too good to be true, it probably is.

IR35 is frustrating, but understanding it protects your income. The freelancers who get caught out are usually those who ignore it until HMRC comes knocking.