How to Tell if You Are Inside or Outside IR35

Understanding whether you’re inside or outside IR35 isn’t about memorising tax law – it’s about recognising how your working relationship actually looks in practice. HMRC focuses on what you do day to day, not what your contract says on paper.

Knowing the signs helps you have informed discussions with clients and agencies, but it’s important to remember that you don’t make the final call. Under current rules, the end client is legally responsible for deciding IR35 status and issuing a Status Determination Statement (SDS).

Your goal is to understand the factors, recognise how they apply to you, and spot potential issues early – even though you may not have the power to change the final outcome yourself.

• IR35 status depends on how you actually work day to day, not just what your contract says
• The three main IR35 tests are control, substitution, and mutuality of obligation – together they determine if your role is truly independent
• The end client is legally responsible for deciding your IR35 status and issuing a Status Determination Statement (SDS)
• You can influence your IR35 position by clarifying project scope, defining deliverables, and maintaining genuine independence from the client
• If you disagree with an SDS, you can formally challenge it in writing and the client must respond within 45 days

If these situations sound familiar, your contract is probably inside IR35:

• You work the same hours as permanent staff and take direction from a manager
• You must request time off or report sickness through the client’s system
• You use the client’s equipment, processes and policies
• You’re part of internal meetings, reviews and performance discussions
• You can’t send anyone else to do the work – the client expects you personally
• The role feels ongoing rather than project-based

If these feel closer to your reality, you’re probably outside IR35:

• You decide how, when and where to deliver the project
• You invoice for defined deliverables rather than time worked
• You could send a qualified substitute if needed
• You supply your own tools or systems
• You’re not embedded in internal management or HR processes

Remember that these are only indicators. They help you understand how HMRC and your client might view the engagement, but the official decision still sits with the end client.

HMRC asks who decides how the work is done, where it’s carried out and when. If the client dictates your daily routine, supervises tasks or can move you between projects, that looks like employment.

If instead you set your own schedule and delivery method, for example choosing your tech stack or work plan, that shows independence.

A genuine business can send another suitably qualified person to deliver the service.

If your contract allows substitution and the client would realistically accept it, that supports an outside IR35 position.

If the client insists only you can perform the work, it suggests they value your labour rather than a business service.

Employees are expected to keep accepting work, and employers must keep providing it. Independent contractors, by contrast, deliver a defined piece of work and can walk away once complete.

If the client expects you to stay indefinitely or keeps offering tasks without a new agreement, HMRC may view the relationship as employment-like.

Remember, these tests explain how status is assessed – they don’t mean you can decide it yourself. The client will apply (or sometimes misapply) the same principles when they issue your SDS.

Many contractors believe a carefully written contract will protect them, but IR35 decisions hinge on what happens in real life.

Even if a contract says you have control and substitution rights, those clauses mean little if, in practice, you follow the client’s hours, attend daily stand-ups and have no real autonomy.

HMRC gives far more weight to behaviour and working culture than to legal phrasing. That’s why you can see two contracts with identical wording assessed differently – because the clients run them differently.

• On paper: “The contractor may determine their own hours”
• In practice: The client expects 9-to-5 attendance and requires advance notice for time off.

Therefore, the result will likely be inside IR35, regardless of what the clause says.

For most contractors, spotting these mismatches early, before onboarding, is the best way to avoid surprises later, even though the client still owns the final determination.

If you’ve already reviewed the checklist above, you’ll have a sense of which side your current contract sits on.

In practice, most engagements show a mix of indicators – a few points that look independent and others that look employment-like.

This overlap creates the grey areas that cause uncertainty for both contractors and clients, and it’s why understanding the tests matter even though the final decision rests with your client.

When the evidence is mixed, most organisations err on the side of caution because they carry the tax risk if HMRC later challenges their decision.

While you can’t issue or override the SDS, you can influence how the engagement is shaped before onboarding:

• Clarify scope early ask whether the work is project-based or time-based
• Define deliverables – make sure outcomes, not daily tasks, are in the statement of work
• Discuss autonomy – explain how you normally deliver and agree boundaries that reflect independence
• Avoid employment-style perks – decline staff benefits or allowances that imply you’re part of the workforce

These steps don’t guarantee an outside determination, but they help clients see a legitimate business-to-business arrangement.

Under the off-payroll working rules, the end client must provide a Status Determination Statement (SDS) explaining whether a role is inside or outside IR35 and the reasons behind that view.

If you disagree, you have the right to raise a formal disagreement through the client’s internal process.

1. Submit your challenge in writing – reference the SDS and explain why you believe it’s incorrect – for example, that you have genuine control or substitution rights
2. Provide evidence – keep it factual and professional: outline specific clauses, working practices or previous assessments that support your view
3. Wait for a written response – the client is legally required to reply within 45 days, either confirming their original decision or issuing a revised SDS

Be aware that this isn’t an appeal to HMRC – it’s a client-led review. Many contractors choose not to escalate because the relationship or renewal prospects matter more than the tax distinction.
Still, it’s worth using the process if you believe the evidence strongly supports an outside position or if the SDS reasoning seems incomplete.

Understanding how IR35 decisions are made helps you read the signs and discuss them confidently, even though the final call always rests with your client.

Knowing where your role sits lets you plan how you’ll work – through your Limited Company for outside IR35 engagements, or via a compliant umbrella arrangement when a client places you inside IR35.

At SG Accounting, we help contractors on both sides of IR35 – from explaining SDS decisions to providing simple umbrella solutions when required.

If you’d like to talk through a current engagement or get clarity on a client’s determination, our team is happy to help.

(Header image: designed by Drazen Zigic – Freepik.com)