IR35 status checker (UK 2026)

How the score works

What this checker doesn't cover

• Chapter 8 vs Chapter 10 determination— who is RESPONSIBLE for getting the determination right (you, the engager, or the agency) depends on whether you're engaging with a small private-sector client (Chapter 8) or a public-sector / medium-large private client (Chapter 10). This checker assesses the underlying status; the responsibility-allocation framework is in gov.uk's IR35 hub and our IR35 guide.
• Specific contract wording: a clause-by- clause review needs a specialist to read your actual agreement. This checker assesses your working pattern from your perspective; it can't see the contract.
• Engager-side determinations(SDS), if your client is on Chapter 10 they make the determination. This checker is for YOUR view. Compare your view with theirs; if they disagree there's a formal client-led-disagreement process to follow.
• Mid-engagement status changes: IR35 status can change during an engagement if working practices drift. Re-run the checker quarterly on long engagements to spot status drift.
• Construction Industry Scheme (CIS): CIS is a different regime for construction subcontractors; similar concepts apply but the rules and consequences differ. Outside this checker's scope.

Frequently asked questions

How is this different from HMRC's CEST tool?

HMRC's Check Employment Status for Tax (CEST) tool is the official version. It's been criticised by tax tribunals and IR35 specialists for two specific weaknesses: (1) it doesn't weight Mutuality of Obligation adequately, despite MOO being a foundational test in case law (Carmichael v National Power; Ready Mixed Concrete v MoP&NI), and (2) it tends to produce 'inside IR35' results in borderline cases. This calculator weights substitution most heavily (per Express & Echo Publications v Tanton, where the Court of Appeal held an unfettered substitution clause was incompatible with employment), gives MOO meaningful weight, and surfaces the case-law rationale per question. Neither tool is legally binding, only a tribunal is. Use both, plus a paid contract review for engagements worth £30k+.

Why is substitution weighted so heavily (40%)?

Case law treats it as the strongest single indicator. In Express & Echo Publications v Tanton (1999), the Court of Appeal held that an unfettered right of substitution was 'inherently inconsistent' with personal service as required for employment. Subsequent cases (MacFarlane v Glasgow City Council, James v Greenwich Council) have consistently applied this logic. A genuine substitution clause that would actually be exercised, not a paper-only provision, is the clearest single fact a tribunal will weigh in your favour. The weighting reflects the legal reality, not just our editorial preference.

What if my contract says one thing but my actual working practices differ?

Working practices override contract wording in case law. HMRC and tribunals look at what actually happens day-to-day, not what the contract claims. A beautifully-drafted contract with substitution rights, no MOO, and full autonomy is worthless if you've been at the same desk for 3 years, take direction from a manager, and have never even discussed substituting. When answering this checker, answer based on actual working practice, not contract wording. If they diverge, fix the working practices BEFORE relying on the contract for IR35 protection.

What does the verdict actually mean?

Outside (70+): Your working pattern points clearly toward self-employment. Operate as a Ltd or sole trader; this is what the contract should support. Borderline (40-69): The pattern doesn't clearly support either side. This is exactly when a paid contract review (£200-£500 from Kingsbridge / Qdos / IR35 Shield) is best value, they'll review the contract AND the working practices and tell you which way to lean. Inside (<40): Your pattern points toward employment. Operating as a Ltd contractor on this engagement risks IR35 reclassification, meaning HMRC can demand back-tax on the deemed salary. Umbrella is generally cleaner for inside-IR35 work; see the inside-vs-outside comparison.

Does this work for the public-sector / large-private-sector cases (Chapter 10)?

Same legal tests, the determination is whether the engagement WOULD be employment if the intermediary (your Ltd) didn't exist. What changes between Chapter 8 (small private-sector clients, you make the determination) and Chapter 10 (public sector + medium/large private clients, the engager makes the determination) is WHO is liable for the deemed PAYE if the determination is wrong. Your status is determined the same way; the consequence of a wrong determination falls in different places. See /guide/what-is-ir35 for the full Chapter 8 vs Chapter 10 breakdown.

I scored borderline, what now?

Three options in increasing order of cost and rigour. (1) Read the rationale per question, borderline often means one or two specific factors are weak (e.g. you've been at the same client for 3+ years with no real substitution). Address those if possible: rotate clients, exercise substitution rights, push back against day-to-day direction. (2) Get a paid contract review (£200-£500) from Kingsbridge / Qdos / IR35 Shield. They review BOTH the contract wording AND the working practices and produce a written opinion you can rely on (and that an IR35 insurer will recognise). (3) IR35 insurance (£200-£500/year via Kingsbridge / Qdos / IR35 Shield) covers the legal cost of an HMRC investigation AND, on most policies, the resulting tax liability. For any engagement worth £30k+, the expected cost of investigation without insurance dominates the premium.

Is the score legally binding?

No. The only legally-binding determination of IR35 status is from a First-tier Tax Tribunal. HMRC's view via CEST is not binding either; it's just HMRC's stated position. A paid contract review is a written professional opinion that gives you a defensible basis if HMRC challenges. This calculator is informational, designed to surface the structural factors and the case-law weight behind each one. Use it as a starting point, not a shield.

What's the 'in-business-on-own-account' (IBOOA) test?

Articulated in Hall v Lorimer (1994). The court asks: 'Is this person genuinely in business on their own account, or are they an employee of the engager dressed up as a contractor?' Markers of being in business on your own account: multiple clients (or genuine pursuit of them), business website / business cards / professional indemnity insurance, separate business bank account, accountant, ability to take on / refuse work, financial risk-bearing. The test is a holistic counter-balance to the three principal tests, even if substitution is fettered and control is high, strong IBOOA evidence can still tip the balance toward self-employment.

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