IR35 Compliance: What Contractors And Companies Need To Do

If you hire contractors (or you’re thinking about it), IR35 can feel like one of those rules you “sort out later”. But IR35 issues with contractors can land on your desk quickly - especially if you’re scaling, bringing in specialist talent, or using long-term contractors to fill key roles.

The tricky part is that IR35 isn’t just about what your contract says. It’s about how HMRC is likely to view the working relationship in practice. And when the off-payroll working rules apply, your company can end up responsible for assessing status, issuing documents, and sometimes running payroll deductions (which are tax compliance steps).

In this guide, we’ll walk you through IR35 in plain English, what “compliance” can look like for small businesses, and practical steps you can take to reduce risk while still benefiting from a flexible workforce. This article is general information only and isn’t tax advice - IR35 outcomes can be fact-specific, so consider getting tailored advice for your situation.

What Is IR35 (And Why Does It Matter When You Hire Contractors)?

IR35 is the name commonly used for the UK’s “off-payroll working” rules. At a high level, it’s designed to reduce “disguised employment” - where someone works in a way that looks like employment, but provides their services through an intermediary (often their own personal service company), potentially paying less tax and National Insurance than an employee would.

For your business, the key question is:

If we removed the intermediary, would this person look like an employee for tax purposes?

If the answer is “yes”, the engagement may be inside IR35. If the answer is “no”, it may be outside IR35.

Why IR35 Risk Is A Business Issue (Not Just The Contractor’s Problem)

Under IR35 reforms for the private sector (introduced in 2021), many businesses that hire contractors are responsible for:

• Making a status determination for the contractor’s engagement;
• Communicating that determination via a Status Determination Statement (SDS);
• Operating a dispute process if the contractor disagrees; and
• Ensuring the correct party deducts tax/NICs where required (often via payroll).

That’s why having a sensible IR35 compliance process is part of good governance - just like having proper hiring paperwork, GDPR practices, and clear commercial contracts.

IR35 Doesn’t Apply In Exactly The Same Way To Every Business

Who carries the responsibility can depend on factors like:

• Whether the contractor is engaged directly or via an agency;
• Whether the contractor provides services through their own limited company;
• Whether your business is considered “small” under the Companies Act tests (which can affect who takes on the IR35 assessment responsibility); and
• The reality of the working arrangements (not just what the contract says).

Because these details matter, it’s worth treating IR35 as a repeatable internal process, rather than a one-off decision you make informally.

When Are Contractors Inside IR35? The Practical Tests You Need To Understand

IR35 status is ultimately about the real working relationship. Contracts matter, but HMRC will look at what happens day-to-day.

While each case is fact-specific, there are a few core themes that show up again and again in IR35 assessments.

1) Control

Ask yourself:

• Do you control how the work is done, or only what needs to be delivered?
• Are they managed like a staff member (hours, tasks, approvals), or treated like an independent specialist?
• Do they have autonomy in the method and timing of delivery?

The more your business controls the “how”, the more the engagement can resemble employment.

2) Substitution (Personal Service)

Genuine contractors are often able to provide a suitably qualified substitute to do the work (subject to reasonable checks for security, quality, etc.).

If the contractor must personally deliver the work and cannot send a substitute, that can point toward “inside IR35” - although substitution clauses need to be genuine in practice, not just words on paper.

3) Mutuality Of Obligation

This concept can be nuanced (and it’s often misunderstood). Broadly, it looks at whether the arrangement creates an ongoing obligation:

• For your business to keep offering work; and
• For the contractor to keep accepting it.

In practice, HMRC and tribunals will usually consider mutuality alongside the other key factors (like control and personal service), rather than treating it as a standalone “tick-box” test. Project-based engagements with clear end points tend to look more like genuine contracting than open-ended “ongoing work as required”.

4) Integration Into Your Business

Consider whether the contractor looks and feels like “part of the team”, for example:

• Having a management title internally;
• Managing employees as if they are a line manager;
• Being on internal org charts;
• Receiving staff benefits (even informally);
• Using staff systems without any contractor boundaries.

If you want to sense-check how these factors play into employment classification more broadly, the distinctions in employment status tests are a helpful reference point - IR35 isn’t identical, but the logic overlaps.

IR35 Compliance Requirements: What Your Company Must Actually Do

“IR35 compliance” sounds like a single requirement, but it’s really a bundle of steps you should be able to evidence. Because these steps often involve tax treatment (PAYE/NICs), you may also want to coordinate with your accountant or payroll provider.

Here’s what that usually looks like in a well-run small business.

1) Identify Which Engagements Could Be In Scope

Start with a simple contractor audit. For each contractor, note:

• Who they contract through (individual, sole trader, limited company, umbrella, agency);
• The length of engagement and whether it’s rolling;
• Whether they’re working like a “role” in your business or delivering a defined project;
• Who supervises them and how the work is directed.

This will help you spot higher-risk arrangements quickly (for example: a contractor working full-time for 12 months, reporting into a manager, performing a BAU role).

2) Make A Status Determination (And Document It)

You’ll generally want a consistent approach to determinations, such as:

• A structured internal questionnaire;
• Evidence of how the role operates in practice;
• Written reasoning recorded in a file (so you can show how you reached your conclusion).

Even where you use HMRC tools, it’s still sensible to record the supporting facts you relied on. If HMRC ever queries your decision, you’ll want to be able to show it was a reasonable, considered determination based on the information available at the time.

3) Issue A Status Determination Statement (SDS)

Where the rules require it, you’ll need to provide an SDS that:

• States whether the engagement is inside or outside IR35; and
• Explains the reasons for that conclusion.

You’ll also need to pass the SDS down the supply chain (for example, to an agency) where relevant.

4) Have A Dispute Process (And Actually Use It)

If a contractor challenges your status decision, you’re expected to:

• Consider the dispute;
• Respond within a reasonable timeframe; and
• Confirm whether you’ve changed your determination or not, with reasons.

From a risk perspective, the goal is to show your business treats determinations seriously and engages with disagreements in good faith.

5) Operate Payroll Deductions If The Engagement Is Inside IR35

If a contractor is inside IR35 and your business is the “fee payer” in the chain, you may need to deduct income tax and National Insurance contributions through payroll (and account for employer NICs where applicable).

This is the point where IR35 becomes very operational - and where businesses can get caught out if they haven’t aligned their finance, HR, and procurement processes.

How To Reduce Contractor IR35 Risk Without Killing Flexibility

Good IR35 management isn’t about avoiding contractors. It’s about engaging contractors in a way that matches the legal reality of the relationship.

Here are practical strategies that can help.

Use Clear, Contractor-Focused Agreements (Not Employee-Style Documents)

Your paperwork should support the intended relationship. For example, a properly drafted Contractors Agreement can help align expectations around deliverables, independence, invoicing, IP, confidentiality, and termination.

Where the engagement is more advisory or project-based, a Consulting Agreement may be more appropriate.

What you want to avoid is copying employment-style clauses into a contractor arrangement (for example, staff benefits, fixed working hours with ongoing obligations, or employee-like reporting lines) unless the reality is truly employment - in which case you may be better off using an Employment Contract and hiring properly.

Design The Engagement Around Deliverables

One of the most common IR35 pain points is hiring a contractor to perform an “ongoing role” rather than deliver a defined output.

Where you can, structure the engagement as:

• A defined project or statement of work;
• Milestones and acceptance criteria;
• Payment tied to outputs (not time spent); and
• A clear end date or review point.

This isn’t about window-dressing. It’s about ensuring you’re actually buying services as a client, rather than managing labour like an employer.

Keep Working Practices Consistent With The Contract

It’s surprisingly easy for day-to-day working practices to drift. For example:

• A contractor starts attending all staff meetings;
• They get given a company job title;
• They’re approved for annual leave “like everyone else”;
• They become the default person for BAU tasks indefinitely.

Those changes may be totally understandable operationally - but they can undermine your original IR35 assessment.

A simple fix is to do periodic “contractor check-ins” internally (quarterly is common), so you confirm the arrangement still matches the intended contractor model.

Manage Confidentiality, IP, And Data Protection Properly

Many contractors will access sensitive business information (customer lists, pricing, product plans, source code, marketing data, and so on). Your contractor contract should cover confidentiality and intellectual property clearly.

Also remember: contractors often handle personal data (even if it’s just email addresses in a CRM). If so, your compliance under UK GDPR matters - and you may need the right wording and policies in place, including a suitable Privacy Policy if you collect and use personal data as part of your operations.

Common IR35 Mistakes Small Businesses Make (And How To Avoid Them)

Most IR35 problems don’t come from bad intentions. They come from speed, growth, and informal arrangements.

Here are some frequent issues we see when businesses hire contractors.

Mistake 1: Treating IR35 As “The Contractor’s Problem”

Even if the contractor is experienced, your business may still have obligations under the off-payroll working rules. If you’re the one required to make the determination, you can’t outsource the responsibility informally.

Mistake 2: Assuming A Limited Company Contractor Is Automatically Outside IR35

The contractor’s business structure doesn’t decide IR35. The working relationship does.

Mistake 3: Using A Generic Template Contract That Doesn’t Match Reality

Templates can be a starting point, but they often miss the nuance that matters for IR35 (control, substitution, deliverables, and the practical boundaries of the relationship).

It’s also worth remembering that even outside IR35, you still want a contract that is enforceable and commercially sensible - the fundamentals of contract law apply regardless of employment status.

Mistake 4: Letting Contractors Become “Permanent Staff By Another Name”

If a contractor is filling a permanent seat, doing ongoing BAU work, managed like staff, and staying for years, IR35 risk increases - and you may also be creating wider legal risk around employment status arguments.

Mistake 5: Not Aligning HR, Finance, And Procurement

IR35 determinations sit at the intersection of legal, finance, and operations. If your hiring manager agrees one thing, finance processes another, and procurement doesn’t track contractors properly, you end up with inconsistency - and inconsistency is where compliance tends to break down.

Key Takeaways

• IR35 issues are about the reality of the working relationship - not just what the contract says and not just how the contractor is paid.
• IR35 compliance usually involves identifying in-scope engagements, making and documenting determinations, issuing an SDS, handling disputes, and applying payroll deductions where required.
• The core IR35 indicators to watch are control, substitution, mutuality of obligation (considered with other factors), and integration into your business.
• You can reduce risk by structuring engagements around deliverables, using the right contractor-focused contracts, and keeping working practices consistent over time.
• Don’t forget the wider legal foundations: contractor arrangements should also cover confidentiality, IP, and data protection so your business is protected from day one.
• If you’re unsure, it’s worth getting tailored legal and tax advice - IR35 outcomes can depend on the fine details of how the contractor actually works in your business.

If you would like help with contractor agreements, IR35-related risk management, or reviewing how you engage contractors, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.