IR35 inside vs outside explained (2026/27)

IR35 is the single biggest tax question for UK limited-company contractors. Get it wrong and you can face a large bill; understand it and you can price and structure your contracts sensibly. This guide explains what “inside” and “outside” mean for 2026/27, who decides, and how status changes your take-home.

What IR35 is actually about

IR35 (the “off-payroll working rules”) exists to stop people working like employees while paying tax like a business. HMRC looks through your limited company at the reality of the working relationship. If — ignoring the company in the middle — you’d look like the client’s employee, the contract is inside IR35 and should be taxed roughly like employment.

Inside vs outside IR35

• Outside IR35: you’re running a genuine business providing a service. You can pay yourself a low salary plus dividends, retain profit, and claim legitimate expenses. This is the tax-efficient position contractors aim for.
• Inside IR35: the income is treated as deemed employment income. Income Tax and National Insurance are deducted much as they would be for an employee, so there’s little room for the salary-plus-dividend efficiency, and your take-home is lower for the same day rate.

The gap can be large. Because inside-IR35 income is taxed close to a salary — Income Tax at 20% to £50,270 then 40%, plus employee NI at 8% between £12,570 and £50,270 and 2% above — you keep noticeably less than on an equivalent outside contract, where dividends are taxed at just 10.75% (basic rate) in 2026/27. Our IR35 take-home calculator shows the difference in pounds for your day rate.

The three tests that decide status

No single factor settles it; HMRC and the courts weigh the whole picture. The three most important tests are:

1. Personal service / substitution. Must you do the work, or can you send a suitably qualified substitute in your place? A genuine, unfettered right of substitution points outside IR35.
2. Control. Does the client direct how, when and where you work, like a boss? A high degree of control points inside. Autonomy over how you deliver points outside.
3. Mutuality of obligation (MOO). Is the client obliged to offer work and are you obliged to accept it, on an ongoing basis? Rolling obligation looks like employment (inside); a defined project with a clear end looks like a business relationship (outside).

Other pointers help too: being in business on your own account (your own equipment, insurance, marketing, several clients, financial risk) supports an outside determination. HMRC’s free CEST tool gives an indicative result, but it isn’t the final word.

Who decides — and who pays if it’s wrong

Since April 2021 the rules changed for the private sector:

• Medium and large clients must assess your status and issue a Status Determination Statement. If they get it wrong, liability for the unpaid tax generally sits with the client or the fee-payer in the chain.
• Small clients (broadly, businesses under two of: turnover £10.2m, balance sheet £5.1m, 50 employees) are exempt — here you (via your limited company) remain responsible for assessing and getting it right, as under the original rules.

This matters for contract disputes: if a large client blanket-assesses roles as inside, that’s their call to make, though a well-evidenced working practice can support a challenge.

Practical takeaways

• Assess each contract on its own facts — status is per engagement, not per person. You can hold outside and inside contracts in the same year.
• Keep evidence. A written contract and actual working practices that show substitution rights, autonomy and no ongoing obligation are your best protection.
• Price for it. If a role is inside IR35, factor the lower take-home into the rate you accept. Model it first with the IR35 take-home calculator.
• Don’t rely on wording alone. A contract that says “outside IR35” means nothing if the day-to-day reality looks like employment.

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This guide is information, not tax or legal advice. IR35 is fact-sensitive and the figures use published HMRC rates for 2026/27. Check gov.uk/guidance/understanding-off-payroll-working-ir35 and consider a specialist IR35 contract review before relying on a status.

Try the tool IR35 Take-Home Calculator Compare your inside vs outside IR35 take-home pay as a UK contractor — day rate to annual net, via an umbrella or your own limited company. Free, no signup. Open the calculator →

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