When Does IR35 Apply When Hiring Contractors in the UK?

If you hire independent contractors or consultants, you’ve probably heard about IR35 (the “off‑payroll working” rules). Knowing when IR35 applies is crucial because, if it does, you may be responsible for operating PAYE and paying employer National Insurance on fees you pay to a contractor’s personal service company (PSC).

In this guide, we’ll explain when IR35 applies, who’s responsible for making the call, the practical tax and cost implications for small businesses, and a sensible step‑by‑step process you can follow before you onboard a contractor.

What Is IR35 And Why It Matters To Small Businesses

“IR35” is a shorthand for UK tax rules designed to identify “disguised employment”. In plain English, HMRC asks: if the contractor hadn’t interposed a limited company or partnership, would they look like your employee for tax purposes? If the answer is yes, IR35 can apply so that PAYE, employee NICs and employer NICs are due on the contractor’s fees.

There are two regimes you’ll hear about:

• IR35 in the contractor’s hands (Chapter 8, Part 2 ITEPA 2003) – historically applied where the contractor decided their own status and accounted for any deemed employment taxes.
• Off‑Payroll Working rules in the client’s hands (Chapter 10) – since 2017 for public sector and since April 2021 for medium and large private sector clients, the end client is responsible for assessing status and, if inside IR35, ensuring PAYE/NICs are operated in the payment chain.

For many small businesses, the off‑payroll rules won’t bite because of the “small company exemption” (more on that below). But even where you’re exempt, the underlying IR35 principles still matter. If your contractor is effectively operating as an employee, HMRC can challenge the arrangement, and you may face tax risk indirectly through your supply chain.

Does IR35 Apply To Your Business? The Core Tests And The Small Company Exemption

Whether IR35 applies turns on two questions: (1) does your business fall within the off‑payroll rules, and (2) looking at the engagement, would it be employment if the intermediary didn’t exist?

1) The Small Company Exemption

Private sector clients that qualify as “small” under the Companies Act 2006 are outside Chapter 10 (off‑payroll) – in that case, the contractor’s PSC remains responsible for IR35. You’re “small” for a financial year if you meet at least two of the following: annual turnover of £10.2m or less, balance sheet total of £5.1m or less, and an average of 50 or fewer employees. If you’re not a company (e.g. an unincorporated business), a simplified turnover test applies.

If you’re medium or large, you must make a status determination for each PSC engagement and pass it down the chain. If you’re small, you don’t have to issue a Status Determination Statement (SDS) – but you should still understand the status factors and structure contractor relationships appropriately.

2) Would The Engagement Be Employment But For The PSC?

HMRC and the courts look beyond labels to the real working practices. Key status factors include:

• Personal service and substitution – are you buying the personal services of a named individual, or can the contractor send a genuinely suitable substitute that you cannot unreasonably refuse?
• Control – who decides how, when and where the work is done? Day‑to‑day control and managerial oversight point toward employment.
• Mutuality of obligation (MOO) – are you obliged to provide ongoing work and is the contractor obliged to accept it, beyond a defined project?
• Financial risk and opportunity – does the contractor bear risk (e.g. fixed‑price project, rectifying defects on their own time) and have a chance to profit?
• Integration – is the contractor “part and parcel” of your team (company email, line management, benefits), or clearly independent?
• Provision of equipment – who supplies the main tools and equipment (beyond security or access kit)?
• In business on their own account – multiple clients, marketing, insurance, their own processes and staff all point to self‑employment.

No single factor is decisive. It’s a holistic assessment of the contract and the working practices. If you need a refresher on how the tests compare, it’s worth revisiting the employment status tests and the difference between worker vs employee.

HMRC’s CEST tool can be a useful data point, but it’s not infallible. Your conclusion should be supported by the contract, onboarding documents and actual working practices.

Roles And Responsibilities In The Supply Chain

Under the off‑payroll rules, responsibilities are allocated as follows:

• Client (you) – for medium/large private sector and public sector, you must take “reasonable care” to determine status and issue a written SDS to the worker and the next party in the chain (e.g. the agency). You must also operate a client‑led disagreement process for status challenges.
• Fee‑payer – the party paying the PSC (often an agency) must operate PAYE and NICs if the SDS says “inside IR35”. If you pay the PSC directly, you’re the fee‑payer.
• Contractor’s PSC – if you’re a small client (so Chapter 10 doesn’t apply), the PSC is responsible for assessing IR35 and paying any deemed employment taxes under Chapter 8.

Liability can move up the chain if paperwork is missing, you don’t take reasonable care, or taxes go unpaid. That’s why status decisions, clear documents and reliable intermediaries matter.

If you engage through multiple tiers (e.g. a consultancy that then provides individuals), consider whether you’re buying a genuine “managed service” (deliverables‑based, supplier autonomy) or simply labour supply. The former points away from employment; the latter often attracts IR35 scrutiny.

IR35 Implications: Tax, Cost And Risk For Clients

If an engagement is “inside IR35” and you’re the fee‑payer:

• You must deduct PAYE and employee NICs from the contractor’s fees (excluding VAT), pay employer NICs (currently 13.8%) and, where applicable, the Apprenticeship Levy.
• The gross invoice from the PSC is adjusted for tax – commercially, you should agree rates on an “inside IR35” basis so there’s no confusion about who bears the cost uplift.
• Being inside IR35 is a tax status only – it does not automatically give the contractor employee rights. Employment status for rights is a separate test under employment law.
• VAT still applies normally if the PSC is VAT‑registered; IR35 does not change VAT liability.

If you mis‑categorise an engagement, HMRC can seek underpaid tax, NICs, interest and penalties. You also risk reputational damage and disputes with contractors. Robust processes reduce that risk and keep your hiring strategy flexible.

A Step‑By‑Step IR35 Assessment Process For Clients

A consistent process helps you reach defensible decisions and stay compliant as you grow. Here’s a practical approach.

Step 1: Define The Engagement Properly

• Set clear deliverables, milestones and acceptance criteria. Use statements of work, not just time‑and‑materials descriptions.
• Agree project‑based fees or outcomes where possible, rather than open‑ended hours that resemble employment patterns.
• Ensure the supplier is genuinely in business on their own account (multiple clients, professional insurance, own equipment where feasible).

Step 2: Draft Status‑Friendly Documents

• Use a well‑drafted Contractor Agreement or Consulting Agreement that reflects the reality of the engagement.
• Include a genuine right of substitution (with practical steps to make it operable), limited control clauses, and provisions that show contractor autonomy and financial risk (e.g. defect rectification at own cost).
• If you source talent via a supplier, ensure your Sub‑Contractor Agreement or agency terms align with your status position and allocate tax risk clearly.

Step 3: Assess Working Practices Against The Tests

• Apply the control, personal service, MOO, financial risk and integration factors to your specific facts. Keep a written record of your reasoning.
• Use tools and checklists, but do not rely on them blindly. If the result is borderline, take tailored advice.
• If you’re a medium/large private sector client, prepare a written SDS and follow a client‑led disagreement process if challenged.

Step 4: Align Onboarding With Your Decision

• Keep contractors separate from employees (no line‑management responsibilities, different benefits, avoid company‑wide perks that signal employment).
• Approve substitutes if the contract allows it and they’re suitably qualified. Operationalising substitution strengthens your position.
• Audit timesheets, sign‑offs and communications to ensure they match the contract and your IR35 rationale.

Step 5: Review Periodically And When Things Change

• IR35 status can change if scope expands, management tightens or project structure drifts. Reassess at key milestones.
• If a role becomes “business as usual” and looks like employment, consider moving to an Employment Contract instead.

Edge Cases To Watch

• Overseas suppliers – if you engage overseas contractors, UK tax withholding can still arise if the work is for a UK client and paid by a UK fee‑payer. Get advice on cross‑border tax and PE risk.
• Small company exemption – if you grow and cease to be “small”, the off‑payroll rules can start to apply from the next tax year. Plan ahead.
• Managed service vs labour supply – buying outcomes with supplier autonomy is different from directing individuals. Document that distinction clearly.

Contracts And Documents To Put In Place

Your legal paperwork should support your status decision and reduce risk through the supply chain. Avoid generic templates – the right wording and structure depend on your facts.

• Contractor Agreement / Consulting Agreement – set scope, deliverables, substitution, control, equipment, IP, confidentiality and liability. Make sure it’s legally binding and reflects actual practice.
• Statement of Work (SoW) – define outputs, milestones, acceptance criteria and pricing model (fixed price where appropriate).
• Supply Chain Terms – if you use agencies or consultancies, flow down IR35 clauses, warranties on status, indemnities for tax, and cooperation on issuing the SDS. Use a robust Sub‑Contractor Agreement where relevant.
• Onboarding Policies – practical guidance for managers so working practices (access, supervision, benefits) align with your IR35 position.
• Status Determination Statement (where required) – a clear, reasoned document setting out your conclusion and the factors you relied on, plus the process for disagreements.

Remember, what happens day‑to‑day carries significant weight. The contract and the reality must line up – if they diverge, HMRC will focus on the reality.

Key Takeaways

• IR35 applies where, ignoring a contractor’s PSC, the engagement would look like employment for tax purposes. Medium and large private sector clients must make status decisions and, if inside IR35, ensure PAYE/NICs are operated.
• Many small businesses benefit from the “small company exemption” so the contractor’s PSC remains responsible – but the same status factors still matter and HMRC can challenge disguised employment.
• Status turns on control, personal service vs substitution, mutuality of obligation, financial risk, integration, equipment and being “in business on own account”. It’s a holistic assessment.
• Inside IR35 means PAYE, employee NICs, employer NICs and potentially the Apprenticeship Levy on the contractor’s fees (VAT treatment is unchanged). It does not automatically grant employment rights.
• Put robust documents in place: a tailored Contractor Agreement or Consulting Agreement, clear SoWs, supply‑chain clauses, and (if required) a well‑reasoned SDS. Align working practices with your status position.
• Build a repeatable process: define the engagement, assess the status factors, document your reasoning, onboard consistently, and review when circumstances change. For complex or borderline cases, get tailored advice before you commit.

If you’d like help assessing a contractor engagement, preparing compliant documents, or setting up a practical IR35 process, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no‑obligations chat.