How to Determine Your IR35 Status: The Employment Status Tests Explained

Your IR35 status is determined by three primary employment status tests, personal service and the right of substitution, control, and mutuality of obligation, applied to the actual working arrangement rather than the wording of the contract. A contract that fails all three tests points to employment, and the engagement falls inside IR35. Passing any one of the three does not automatically place you outside, because status is judged in the round, taking the whole picture into account. The IR35 rules 2026 UK contractors work under have not changed the tests themselves; what has changed is who carries the risk when the assessment is wrong. Blue Tick Accountants, a Guildford-based UK tax advisory and accountancy practice, reviews contractor engagements against these tests every week and finds the same weak points recurring. This guide explains each test, how HMRC applies it, what the CEST tool can and cannot tell you, and the practical steps that reduce your exposure.

Key Takeaways

• IR35 status is determined by three primary employment status tests: personal service and the right of substitution, control, and mutuality of obligation.
• Under the off-payroll working rules, the end client determines IR35 status where the client is a medium or large business in the private sector, or any public sector body.
• Small private sector clients are exempt from the off-payroll working rules, and the contractor's own limited company remains responsible for determining status and accounting for any tax due.
• A private sector company is classed as small for off-payroll working purposes if it meets two of three conditions: annual turnover of £10.2 million or less, a balance sheet total of £5.1 million or less, or 50 employees or fewer.
• HMRC judges IR35 status on the actual working practices between contractor and client, not on the written contract, and a contract that does not reflect reality carries no protection.
• HMRC will stand behind a CEST result only if the information entered is accurate and the working practices match it, and CEST returns an undetermined outcome in roughly one in five cases.

What are the three employment status tests for IR35?

The three employment status tests for IR35 are personal service and the right of substitution, control, and mutuality of obligation, and they derive from decades of employment case law rather than from tax legislation itself. HMRC and the tribunals treat these as the irreducible minimum: if any one of them is genuinely absent, an employment relationship cannot exist.

Personal service asks whether you must perform the work yourself. If your contract permits you to send a suitably qualified substitute, and the client cannot unreasonably refuse, you are supplying a service rather than yourself. Control asks who decides what, how, when and where the work is done. A client who directs your working method day to day is behaving as an employer. Mutuality of obligation asks whether the client is obliged to offer work and you are obliged to accept it. A genuine contractor completes the defined engagement and walks away, with no expectation of a rolling pipeline.

Beyond these three, tribunals also weigh secondary factors: financial risk, provision of your own equipment, the right to profit from sound management, and whether you are integrated into the client's organisation. For a full overview of the regime and how the rules developed, see our guide to IR35.

Who decides your IR35 status in 2026/27?

The end client decides your IR35 status where the client is a public sector body or a medium or large private sector business, and the contractor's own limited company decides where the client is a small private sector business. That split determines who pays if the assessment is later found to be wrong.

Where the off-payroll working rules apply, the client must issue a Status Determination Statement setting out the conclusion and the reasoning behind it, and must pass it to both you and any agency in the chain. Liability for unpaid tax and National Insurance sits with the fee-payer, usually the agency or the client, not with you. Where the client is small, the original IR35 legislation in Chapter 8 of ITEPA 2003 still applies, and your company must assess the engagement and account for a deemed employment payment if it falls inside.

A private sector client is small if it meets two of three conditions: turnover of £15 million or less, balance sheet total of £7.5 million or less, or 50 employees or fewer. Many contractors assume small-client status without checking, and that assumption is where the off-payroll working IR35 risk concentrates. Ask the client to confirm its size in writing before you accept the engagement.

How much does being inside IR35 actually cost you?

Being inside IR35 costs a contractor more, and the loss is larger than a single year's tax comparison suggests, because the real advantage of working outside IR35 is control over when profit is drawn. A deemed employment payment is taxed in full in the year it arises. Profit left in a company is not, and that timing difference is where most of the money sits once the salary and dividends rates are as close as they now are.

Consider a contractor billing £500 per day for 220 days, giving turnover of £110,000 in 2026/27. Outside IR35, the company might pay a salary of £12,570, deduct £5,000 of genuine business expenses, and pay corporation tax on the balance before distributing dividends. Inside IR35, where the client is medium or large, the fee-payer treats the full £110,000 as a deemed direct payment subject to PAYE and both employee and employer National Insurance. The 5% deduction that softens the charge where a contractor's own company applies the older Chapter 8 rules is not available on an off-payroll engagement.

Inside IR35, the deemed payment is £96,304 after employer National Insurance, producing £25,954 of income tax and £3,937 of employee National Insurance, leaving £66,414. There is no choice about the timing.

Outside IR35, the company pays £20,443 of corporation tax on profit of £91,295, leaving £70,851 of distributable reserves alongside the £12,570 salary. What happens next decides the size of the gap:

• Draw the whole £70,851 as dividends in the same tax year and £33,151 of it is pushed into the 35.75% upper rate. Take-home is £67,571, only £1,157 ahead.
• Draw £37,700 of dividends in the first year, keeping every pound at the 10.75% ordinary rate, and take the remaining £33,151 in a quieter following year against a fresh personal allowance and basic rate band. Take-home across the two years is £77,264, or £10,850 ahead.
• Retain the reserves and extract them on a solvent liquidation qualifying for Business Asset Disposal Relief, and £67,851 is taxed at 18% rather than 35.75%. Take-home is £71,208, or £4,794 ahead.

The second and third routes are why inside IR35 hurts. Not the headline rates, which have converged, but the loss of every lever that lets a contractor smooth income across tax years, use two personal allowances instead of one, or convert retained profit into a capital gain. None of that survives a deemed payment.

Both the smoothing and the liquidation routes carry conditions. Smoothing only works if the later year genuinely has spare basic rate band, so it suits a contractor winding down, taking a career break or moving to a lower-paid role rather than one billing at the same rate every year. Business Asset Disposal Relief requires a two-year qualifying period and a genuine cessation, and the anti-phoenixing rules will recharacterise the distribution as a dividend if a similar trade restarts within two years. Employer pension contributions remain deductible in both scenarios and become the main remaining lever once an engagement is inside.

Can you rely on HMRC's CEST tool?

HMRC will stand behind a CEST result provided the information entered is accurate and the working practices match what was declared, but CEST cannot reach a conclusion in roughly one in five cases and does not test mutuality of obligation at all.

Check Employment Status for Tax is HMRC's free online tool, and it is the starting point most clients use. Its central weakness is well documented: CEST assumes mutuality of obligation exists in every engagement, which is precisely the test that several contractors have won on at tribunal. A tool that omits one of the three primary tests cannot be treated as the final word.

Use CEST, print the result, and keep it with the engagement file. Then treat it as one piece of evidence rather than a defence in itself. Where the answer is borderline, or where CEST returns undetermined, an independent contract and working practices review carries considerably more weight in an IR35 contractor HMRC enquiry. The tool records what you told it; the enquiry examines what you actually did.

What practical steps reduce your IR35 risk?

The most effective step a contractor can take is to align the written contract with the working practices and keep contemporaneous evidence that the two match, because HMRC tests reality rather than paperwork.

Start with the contract: secure a genuine, unfettered right of substitution, define the deliverable rather than the hours, and remove any notice period that implies ongoing obligation. Then make the working practices match. Decline the client's internal training, keep off the staff social calendar, avoid the company email signature, and do not appear on the organisation chart. Each of those points of integration has been cited in tribunal decisions.

Keep a file for every engagement containing the signed contract, the Status Determination Statement where one applies, any CEST output, correspondence confirming the client's size, and notes on how the work was actually delivered. Consider IR35 insurance covering enquiry costs and tax liabilities, which typically costs a few hundred pounds a year. Above all, assess each engagement separately. Status attaches to the contract, not to you, and a contractor can hold outside and inside engagements simultaneously.

Frequently Asked Questions

How do I know if I am inside or outside IR35?

You are inside IR35 if the engagement, stripped of the limited company, would look like employment when tested against personal service, control, and mutuality of obligation. If you must do the work personally, the client directs how and when you work, and both sides expect work to continue being offered and accepted, the engagement is inside. Assess each contract separately, because status attaches to the engagement rather than the contractor.

Who is liable for unpaid tax if my IR35 status is wrong?

Liability depends on who made the determination. Where the off-payroll working rules apply, because the client is a public body or a medium or large private business, the fee-payer, usually the agency or client, is liable for the unpaid PAYE and National Insurance. Where the client is a small private sector business, your own limited company made the assessment and carries the liability, including interest and potential penalties.

Does a substitution clause guarantee I am outside IR35?

No. A substitution clause only helps if the right is genuine and unfettered in practice. HMRC and tribunals routinely disregard clauses that the client would never actually honour, that require client approval on unreasonable terms, or that the contractor has never attempted to use. A real right of substitution, ideally one you have exercised at least once, is strong evidence. A clause on paper that everyone knows is decorative is worth nothing.

What is a Status Determination Statement?

A Status Determination Statement is the written conclusion a client must issue when the off-payroll working rules apply, setting out whether the engagement is inside or outside IR35 and the reasons for that conclusion. The client must take reasonable care in reaching it and pass it to the contractor and any agency in the chain. If the client fails to issue one, liability for the tax remains with the client.

Can HMRC open an IR35 enquiry into past contracts?

Yes. HMRC can typically go back four years where reasonable care has been taken, six years for carelessness, and up to 20 years where behaviour is deliberate. That reach is why contemporaneous evidence matters: a contract review and working practices note prepared at the time of the engagement is far more persuasive than a reconstruction attempted years later under enquiry.

How Blue Tick Can Help

Blue Tick Accountants reviews contractor engagements against the three employment status tests, examines both the written contract and the working practices, and gives you a clear, evidenced view of where each engagement sits before HMRC asks. Where an engagement is inside IR35, the focus shifts to legitimate mitigation, primarily employer pension contributions and correct expense treatment, so that the cost is contained rather than simply absorbed. Head to our website and book a meeting now.

Conclusion

IR35 status turns on how you actually work, not on how the contract is drafted, and the three employment status tests are the framework HMRC and the tribunals apply. Assess each engagement on its own facts, confirm in writing whether the client is small before assuming responsibility for the determination, and keep evidence at the time rather than reconstructing it under enquiry. A contract review before you sign costs a fraction of an IR35 settlement, and on a £110,000 engagement the difference runs from around £1,200 a year to nearly £11,000 depending on how profit is drawn.

About the Author

This guide was written by Leon, founder of Blue Tick Accountants, a Guildford-based UK tax advisory and accountancy practice that helps limited company owners, contractors, landlords and the self-employed across the UK. It was last reviewed for the 2026/27 tax year.

This article is intended for general informational purposes only and does not constitute tax, legal, or financial advice. Tax rules are subject to change and their application will depend on your individual circumstances. You should always seek advice from a qualified professional before taking action. Blue Tick Accountants accepts no liability for decisions made on the basis of this content.