IR35 in 2026: The 14-Clause Contract Checklist Every UK Freelancer Needs
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. And more importantly: why each clause actually matters.
Quick Background: What IR35 Is Trying to Catch
HMRC invented IR35 to stop "disguised employment" — where someone is effectively working as an employee (same desk, same hours, same boss) 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, and are you obligated to accept it?
If all three look like employment, you're probably inside IR35. Your contract is evidence — but HMRC also looks at the actual working arrangements. Both have to tell the same story.
The 14-Clause Checklist
1. Right of Substitution ⭐ (Most Important)
Your contract should explicitly say you can send a qualified substitute to do the work — and the client can't unreasonably refuse.
Why it matters: A genuine business can send another person. An employee can't.
Common problem: Substitution clauses that require absolute client approval (meaning they can refuse for any reason). HMRC sees through these.
✅ Clause should say: right to substitute, approval cannot be unreasonably withheld, you pay the substitute, you remain responsible for the quality.
2. Control Over Method
The client specifies what gets delivered. You determine how you deliver it.
If your contract gives the client the right to redirect your work at will, supervise your daily tasks, or specify your working processes in detail — that's control, and control = employment indicator.
3. No Mutuality of Obligation
Your contract is for a specific project or period. The client isn't obliged to offer more work, and you're not obliged to accept it.
Open-ended rolling contracts that just keep renewing are a risk here — both parties need genuine freedom to walk away.
4. Deliverables-Based Scope
The contract should specify outputs, not time attendance. "Develop the payment integration module by [date]" is better than "provide development services as required".
Payment linked to deliverables or milestones = stronger outside-IR35 position.
5. Your Own Equipment
You use your own laptop, software, and tools. If the client provides equipment (sometimes required for security/system access), the contract should explain why — not just normalise it.
6. Financial Risk
Genuine businesses carry financial risk. Your contract should reflect this:
- You have professional indemnity insurance (and the contract references it)
- You're liable to fix defective work at your own cost
- No sick pay, holiday pay, or income guarantee
7. No Exclusivity
You're free to work for other clients during the engagement. Non-compete clauses should be time-limited and reasonable — not a broad ban on working in your sector.
Bonus: actively having other clients during any engagement is strong evidence of genuine self-employment.
8. Not Integrated Into the Organisation
Watch out for:
- Being given a company email address as your primary contact
- Being listed in the staff directory
- Attending company all-hands events as a "team member"
These aren't always avoidable, but the contract shouldn't imply you're part of the organisation when you're not.
9. Sensible Termination Clauses
Either party can terminate on reasonable notice. No employment-style protections — no provisions that mirror redundancy rights, no requirement for "cause".
10. Flexible Working Hours and Location
No prescribed 9-5. No mandatory five-day-a-week on-site. You determine when and where you work, subject to availability for agreed meetings and deadlines.
11. Invoice-Based Payment
You raise invoices. The client doesn't generate payslips. Payment terms are business-to-business (e.g., 30 days from invoice). If you're VAT-registered, VAT is charged.
Salary-style monthly payments on a fixed date = employment signal.
12. Contract in Business Name
You're contracting as a business entity, not as an individual. The contract should show your company name or trading name, your business address, and you should invoice from a business bank account.
13. Commercial Dispute Resolution
Disputes are resolved through commercial mechanisms — negotiation, mediation, then arbitration. Not employment tribunal procedures.
14. Status Determination Statement (for medium/large clients)
If your client is a medium or large company, they must issue a Status Determination Statement (SDS) — HMRC's formal assessment of your IR35 status for this engagement.
Ask for it before you start. If they assess you as inside IR35 and you disagree, use their formal disagreement process. Keep a copy.
The Most Important Thing: Contract AND Reality
A contract with all 14 clauses above won't protect you if the reality is different.
HMRC investigators ask:
- Have you ever actually substituted someone? Or is it just a theoretical clause?
- Do you work 9-5 in the client's office every day like an employee?
- Are you actively working for other clients during this engagement?
The contract is evidence of the intended relationship. The actual working arrangements are evidence of the real relationship. Both need to say the same thing.
Free Tools
- IR35 Guide for UK Freelancers — Full background, rules, and risk assessment
- Freelance Contract Template Guide — What to include in contracts generally
- Day Rate Calculator — Check if your rate reflects the IR35 risk you're taking
Written by Landolio — free tools and guides for UK freelancers.
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