IR35 Compliance: Off-Payroll Working Rules In The UK

If your business engages contractors (especially via their own limited companies), IR35 should be firmly on your radar. Since the private sector reforms in April 2021, many clients - not just contractors - carry legal obligations and potential tax risk if an engagement is caught by the off-payroll working rules.

The good news? With a bit of structure, clear processes and well-drafted contracts that reflect reality, you can manage IR35 compliance confidently and keep working with flexible talent.

In this guide, we explain what IR35 is in plain English, when it applies to your business, how to run compliant assessments, what to include in your contractor paperwork, and the key risk factors HMRC looks for.

What Is IR35 And Why Should Small Businesses Care?

IR35 (often called the “off-payroll working rules”) is HMRC’s framework to identify “disguised employment” - situations where a contractor works like an employee but is paid through an intermediary (usually their personal service company, or PSC) to reduce tax and National Insurance Contributions (NICs).

The rules sit in the Income Tax (Earnings and Pensions) Act 2003 and were tightened by the Finance Act 2020. In broad terms:

• If IR35 applies (“inside IR35”), payments must be treated as employment income, with PAYE and NICs deducted.
• If IR35 doesn’t apply (“outside IR35”), the contractor is taxed as a genuine independent business.

Why you should care as a client: for medium and large private sector clients (and all public sector clients), the end client must assess the contractor’s status, take “reasonable care,” issue a Status Determination Statement (SDS), and ensure tax is correctly operated if the role is inside IR35. Failure can lead to tax, NICs, interest and penalties - and in some chains, liabilities can transfer back to the client for non-compliance.

Does IR35 Apply To My Business?

Start by working out if you (as the client) are responsible for IR35 determinations. This depends on your size and the engagement structure.

Small Business Exemption (Private Sector)

In the private sector, “small” companies (as defined by the Companies Act 2006) are exempt from the reformed off-payroll rules. Your engagement is generally assessed by the contractor’s PSC instead if you are small.

You are “small” if you meet at least two of the following in a financial year:

• Turnover of £10.2m or less
• Balance sheet total of £5.1m or less
• 50 employees or fewer

For groups or connected entities, you assess the size on a consolidated basis. If you are not small (i.e., you are medium or large), you must operate the reformed rules.

Engagement Structure Matters

• PSC/intermediary: IR35 focuses on engagements via an intermediary (usually a limited company owned by the contractor). If you contract direct with a sole trader, IR35 as such doesn’t apply - but employment status and PAYE risks still exist under general law.
• Umbrella company: If the contractor is employed by an umbrella company, IR35 typically isn’t in play (the umbrella runs PAYE), but you still need to manage supply chain risk.
• Overseas contractors: IR35 is a UK tax regime. If you’re engaging overseas contractors, different tax, employment and compliance questions arise - IR35 may not apply, but you still need to manage status, IP and data protection risks.

How To Get IR35 Compliance Right: A Step-By-Step Process

Think of IR35 as both a legal test and an operational process. Here’s a practical approach most SMEs can implement.

1) Identify In-Scope Engagements Early

• Flag any roles where you plan to contract with a PSC or intermediary.
• Capture basic facts: job title, services, duration, working practices, supervision/management level, location, who supplies equipment, substitution rights, and deliverables.

2) Conduct A Status Assessment With Reasonable Care

HMRC expects “reasonable care” in reaching a determination. In practice, that means using a robust assessment method, documenting evidence and avoiding blanket decisions.

• Use a structured questionnaire and have the hiring manager provide factual input on day-to-day working practices.
• Consider HMRC’s CEST tool as one input, but don’t rely on it blindly - record why you agree or disagree with its output if the facts are nuanced.
• Reference key status factors HMRC and tribunals consider (explained below), not just contract wording.

Need a refresher on employment status indicators? Our guide to employment status tests walks through control, mutuality of obligation and other core factors.

3) Issue A Status Determination Statement (SDS)

For medium/large clients, you must provide an SDS to the contractor and (if relevant) the next party in the chain (e.g., an agency). The SDS should:

• State whether the engagement is inside or outside IR35, and
• Explain the reasons, referencing the facts gathered.

Keep a copy of the SDS and evidence of how it was shared (e.g., email trail), and store your supporting assessment notes.

4) Operate PAYE/NICs If Inside IR35

If your SDS says “inside IR35,” the “fee-payer” (the party paying the PSC) must deduct PAYE and NICs and account for employer NICs (and possibly Apprenticeship Levy). If you pay through an agency, confirm who the fee-payer is and ensure they have the right payroll setup. Build this into commercial pricing so there are no surprises.

5) Put The Right Contracts In Place

Contracts won’t override facts, but they do matter. Use a clear, tailored Contractor Agreement and service-specific statements of work that match actual working practices. Avoid generic templates and make sure the commercial team understands how contract terms tie to IR35 status.

6) Create A Client-Led Disagreement Process

You’re required to have a process to deal with contractor disagreements about your SDS. Respond within 45 days with either a new SDS or reasons the original stands. Keep a log of challenges and responses to demonstrate reasonable care.

7) Monitor, Review And Adapt

• Reassess status if the role or working practices change (e.g., contractor moves to full-time hours, becomes embedded in your team, or supervision increases).
• Run periodic internal audits, especially on long-running engagements.
• Train hiring managers so they don’t inadvertently change working practices in a way that undermines the status you’ve determined.

What Should Your Contractor Contracts Include?

Well-drafted paperwork helps align expectations, supports the factual position, and reduces wider legal risks beyond IR35. At minimum, consider including:

• Status and tax: A clear status clause (contractor is an independent business), contractor responsibility for their own tax (outside IR35), and fee-payer obligations if inside IR35.
• Control and deliverables: Project-based scope, milestones, output-focused specification and the contractor’s control over how work is performed.
• Right of substitution: A genuine right to provide a suitably qualified substitute at the contractor’s cost, with a sensible consent mechanism.
• Equipment and expenses: Who supplies equipment and how expenses are handled. Independence is stronger where the contractor uses their own kit.
• Financial risk and insurance: Responsibility for rectifying defects at their own cost where reasonable and professional indemnity/public liability insurance requirements.
• Integration: No entitlement to employee benefits, holidays or performance reviews, and clarity that the contractor can work for others (subject to confidentiality and conflicts).
• Confidentiality and IP: Robust confidentiality terms and clear IP assignment so your business owns the deliverables. If you’re engaging creatives or developers, pair this with an IP and contractors review.
• Data protection: If the contractor processes personal data for you, include a compliant Data Processing Agreement.
• NDA and pre-contract safeguards: Before scoping a project, a Non-Disclosure Agreement helps protect sensitive information.

Remember: contracts should reflect actual working practices. If your managers supervise day-to-day, set working hours, and treat the contractor like an employee, a substitution clause on paper won’t keep you outside IR35. Align behaviour with the paperwork.

Common IR35 Risk Factors HMRC Looks For

IR35 status is judged on the reality of the relationship. These are the classic indicators - none is decisive on its own, but together they paint a picture.

Control

Who decides how, when and where the work is done? A high degree of supervision, direction and control suggests employment. Outside IR35 engagements are typically outcome-based with autonomy over method and schedule.

Substitution

A genuine, exercisable right to send a suitably qualified substitute (not just theoretical) points towards business-to-business services. If the work is inherently personal and substitution wouldn’t be permitted in practice, that leans employee-like.

Mutuality Of Obligation (MOO)

Is there an ongoing obligation to offer work and accept it? Open-ended, continuous work with guaranteed hours can look like employment. Project-based statements of work, with defined deliverables and no obligation to offer/accept beyond the scope, point the other way.

Financial Risk

Employees face little to no financial risk. Contractors who price by project, fix defects at their own cost (if they fall short of agreed standards), maintain insurance and have a real chance of profit/loss look more like independent businesses.

Part And Parcel Of The Organisation

If the contractor is embedded in your org chart, manages your staff, uses only your equipment, attends all-hands, and is indistinguishable from employees, HMRC may view them as inside IR35.

Exclusivity And Multiple Clients

Contractors serving multiple clients and marketing their services publicly are less likely to be employees. Genuine freedom to work elsewhere (subject to conflicts) helps.

Want a broader refresher on status beyond IR35 labels? Compare worker vs employee definitions and the knock-on effects for employment rights and obligations.

Supply Chain, Liability And “Fee-Payer” Responsibilities

In chains involving agencies:

• The end client must make the SDS and pass it down the chain.
• The “fee-payer” (the party paying the PSC) must operate PAYE/NICs if the role is inside IR35.
• If parties fail to meet obligations (e.g., missing SDS or unpaid taxes), liability can transfer back up the chain. Be careful who you contract with and perform due diligence.

Commercially, factor in employer NICs and any Apprenticeship Levy when pricing inside IR35 roles, and ensure your contracts apportion risk clearly with agencies and suppliers. If you’re juggling multiple suppliers (e.g., a consultancy who then appoints a specialist), clarify who is the contractor vs subcontractor and align IR35 responsibilities accordingly. If that’s your setup, it’s worth reading our short guide on contractor vs subcontractor arrangements.

Record-Keeping, Audits And Disputes

Good records are your safety net if HMRC asks questions later. Build a tidy paper trail for each engagement:

• Scope and business case for using a contractor rather than employment
• Completed status questionnaires and evidence of “reasonable care”
• The SDS and delivery receipts to the contractor and supply chain
• Contracts and statements of work, plus any substitutions exercised
• Notes of working practices (e.g., who provided equipment, how supervision works)
• Payroll records if inside IR35, including who acted as fee-payer
• Disagreement challenges and your responses within 45 days

Schedule periodic reviews for long-running engagements. If a contractor gradually becomes more integrated into your business, re-run the assessment and issue an updated SDS. It’s far better to correct course early than face unexpected tax assessments later.

Practical Tips To Stay Compliant Without Killing Flexibility

• Design roles from the outset with IR35 in mind - outcome-based deliverables, autonomy over method, and limited day-to-day supervision where feasible.
• Use project-based pricing and distinct statements of work, rather than rolling, time-based assignments that never end.
• Encourage a genuine right of substitution and be prepared to accept a competent substitute where the nature of the work allows.
• Avoid employee-style benefits, appraisals and internal HR processes for contractors.
• Train hiring managers - IR35 compliance lives or dies in working practices, not just the contract.
• Protect your commercial position with clear legals: a tailored Contractor Agreement, IP assignment and confidentiality, and data clauses where personal data is processed.

If you ever shift a contractor into employment, be ready with the right documentation and onboarding. For status-sensitive roles, it’s sometimes safer to employ from day one. Our team can also help you compare contract vs employment against your risk appetite and budget using plain-English status tests and scenario planning.

Beyond IR35: Other Legal Considerations When Using Contractors

IR35 isn’t the only piece of the puzzle. Keep an eye on these areas too:

• Intellectual property: Make sure your agreements include a clean assignment of IP in the deliverables - see our primer on IP and contractors.
• Confidentiality and data: Use NDAs at the scoping stage and a compliant Data Processing Agreement if the contractor handles personal data.
• Right-to-work and compliance: Confirm identity, right-to-work (if applicable), and any sector-specific licences or clearances.
• Insurance and health & safety: Require appropriate insurance and make sure workplace health & safety duties are addressed.
• International engagements: If you plan on engaging overseas contractors, factor in cross-border IP, tax withholding, data transfers and export-controls risks.

Key Takeaways

• IR35 assesses whether a contractor working via a PSC is, in reality, providing employee-like services. Medium and large private sector clients must assess status, issue an SDS and ensure PAYE/NICs are operated for inside IR35 roles.
• Small private sector companies are generally exempt from the reformed rules; in those cases, the contractor’s PSC assesses IR35. Check your size status each year against Companies Act thresholds.
• Build a repeatable process: early triage of PSC engagements, a documented status assessment with reasonable care, an SDS, a 45-day disagreement process and periodic reviews.
• Contracts matter but can’t override reality. Use a tailored Contractor Agreement, align working practices with the paperwork, and include IP assignment, confidentiality and a Data Processing Agreement where personal data is involved.
• HMRC looks at control, substitution, mutuality of obligation, financial risk and how integrated the contractor is. Train managers so day-to-day behaviours support your status decision.
• Keep strong records. If HMRC asks questions, your assessment notes, SDS trail, contracts and working-practice evidence will be critical.
• For complex chains or overseas set-ups, tighten supply chain contracts, clarify who the fee-payer is and consider specialist advice early.

If you’d like help setting up IR35 processes, drafting a robust Contractor Agreement or sense-checking a tricky status call, you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.