IR35 has been a fixture of UK contracting life since 2000, but it's still catching people out — not because the rules have suddenly changed, but because contracts keep not matching the actual working arrangements.
If you're a freelance developer, consultant, or contractor in the UK, here's the checklist every contract you sign should pass.
Quick Background: What IR35 Is Trying to Catch
HMRC invented IR35 to stop "disguised employment" — where someone is effectively working as an employee but billing through a limited company to pay less tax.
The three factors HMRC weighs most heavily:
- Substitution — Can you send someone else to do the work?
- Control — Does the client dictate how you work, not just what you deliver?
- Mutuality of obligation — Is the client obligated to keep offering work?
The 14-Clause Checklist
1. Right of Substitution ⭐ (Most Important)
Your contract should say you can send a qualified substitute — and the client can't unreasonably refuse.
2. Control Over Method
The client specifies what gets delivered. You determine how.
3. No Mutuality of Obligation
The client isn't obliged to offer more work. You're not obliged to accept it.
4. Deliverables-Based Scope
Specify outputs, not time attendance.
5. Your Own Equipment
You use your own laptop, software, and tools.
6. Financial Risk
PI insurance, liable to fix defects at your own cost, no sick pay or holiday pay.
7. No Exclusivity
You're free to work for other clients during the engagement.
8. Not Integrated Into the Organisation
No company email as primary contact, not in the staff directory.
9. Sensible Termination Clauses
Either party can terminate on reasonable notice. No employment-style protections.
10. Flexible Working Hours and Location
No prescribed 9-5. You determine when and where you work.
11. Invoice-Based Payment
You raise invoices. The client doesn't generate payslips.
12. Contract in Business Name
You're contracting as a business entity, not an individual.
13. Commercial Dispute Resolution
Negotiation, mediation, arbitration — not employment tribunal.
14. Status Determination Statement
For medium/large clients, get the SDS before you start.
Contract AND Reality Must Match
A contract with all 14 clauses won't protect you if the reality is different. HMRC investigators look at both the contract and what actually happens day to day.
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Written by Landolio — free tools and guides for UK freelancers.
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