IR35 Guidance: Off-Payroll Working Rules Explained

If you regularly bring in freelancers or consultants through their own limited companies, IR35 is on your risk list. The off‑payroll working rules determine whether your contractor should really be treated like an employee for tax purposes - and if you get it wrong, HMRC can pursue you for unpaid PAYE, NICs, interest and penalties.

Don’t stress - with a clear process, sensible contracts and good records, you can manage IR35 risk confidently. This guide breaks down IR35 in plain English for small businesses, with practical steps to help you make compliant decisions and keep your projects moving.

What Is IR35 And Why It Matters For Your Business?

“IR35” is shorthand for the UK’s off‑payroll working rules. In simple terms, it asks: if the contractor were working directly for you (not through their personal service company), would they be an “employee” for tax purposes? If yes, IR35 applies, and the “fee‑payer” in the chain must operate PAYE and pay employer NICs.

Key points to understand:

• IR35 sits in Chapter 8/Chapter 10 of the Income Tax (Earnings and Pensions) Act 2003, and the April 2021 reforms extended “client responsibility” beyond the public sector to most medium and large private sector clients.
• In the private sector, if you are a medium or large client, you must decide the worker’s status and issue a Status Determination Statement (SDS). The “fee‑payer” (often your business or an agency) must account for PAYE and NICs where the assignment is “inside IR35”.
• If you are a “small company” under the Companies Act thresholds, the contractor’s own company remains responsible for assessing IR35 (more on the small company exemption below).

Why it matters: getting IR35 wrong can be expensive. HMRC can look beyond labels, marketing and job titles and assess the reality of the working relationship. You need a repeatable method for making status calls and documenting your reasoning.

Are You Caught By The Off-Payroll Working Rules?

First, work out whether you (as the client) must make the IR35 status decision or whether the contractor’s company is responsible.

The Small Company Exemption

In the private sector, you’re exempt from the off‑payroll rules if you’re “small” (broadly, two out of three of the following in a financial year):

• Turnover not more than £10.2m
• Balance sheet total not more than £5.1m
• Average employees not more than 50

If you’re small, you don’t have to issue an SDS and operate PAYE for off‑payroll assignments - the contractor’s personal service company decides status and deals with tax. However, you still need to manage wider risks (for example, claims around worker vs employee status for employment rights, even if IR35 doesn’t apply).

If You Are Medium Or Large

If you’re not small, you must:

• Take reasonable care to determine the contractor’s tax status for each engagement.
• Provide a written SDS to the contractor and the party you contract with.
• Operate a disagreement process if the contractor challenges your decision.
• Ensure the fee‑payer deducts PAYE and NICs for “inside IR35” assignments.

Note: “Reasonable care” means a real, case‑by‑case assessment - not blanket policies. HMRC expects you to consider the contract and how the work is actually performed.

How To Make A Status Determination (That Stands Up To Scrutiny)

Status is driven by the overall picture, not one clause. HMRC and tribunals look at factors indicating employment vs genuine self‑employment. The major tests are broadly aligned with employment status principles, applied to the hypothetical direct relationship between you and the individual.

1) Control

Who decides how, when and where the work is done? The more you direct day‑to‑day tasks, set hours, and require approval of methods, the more “employment‑like” it looks. Project‑level outcomes with genuine autonomy suggest contractor status.

2) Substitution

Is there a real right to provide a suitably qualified substitute - and could it happen in practice? A genuine, unfettered right of substitution (with the contractor responsible for payment and onboarding) points away from employment. A clause that exists on paper but would never be allowed in reality carries little weight.

3) Mutuality Of Obligation (MOO)

In an employment‑type relationship there’s an expectation that you’ll provide continuous work and the individual will accept it. A defined statement of work with clear deliverables and no obligation to offer or accept further work supports contractor status.

4) Integration And Equipment

If the individual is embedded in your organisation - using your internal systems as staff, listed on org charts, managing your employees, attending regular staff meetings - that points to employment. Using their own tools and methods, and being kept at arm’s length, supports outside IR35.

5) Financial Risk And Opportunity

Employees are generally insulated from financial risk. Contractors who can make a profit or loss on a project (e.g. fixed‑price quotes, responsibility for remedying defects on their time, own insurances) look less like employees.

6) The Written Contract vs Reality

The contract matters - but HMRC will test what actually happens. Align your day‑to‑day practices with the written terms, and avoid creeping changes that erode independence over time.

Use Tools, But Don’t Rely On Them Alone

You can use HMRC’s CEST tool as part of your process, but it doesn’t cover every nuance. Record your reasoning, save evidence (organograms, project plans, statements of work), and revisit status if the engagement changes. If you’d like a carefully drafted Contractor Agreement that reflects your intended working practices, get that in place before the assignment starts.

What To Put In Your Contracts And Processes

Good documentation won’t “fix” an employment‑like engagement, but it will make genuine contractor arrangements clearer and easier to defend. Consider both the contract and your internal processes.

Core Contract Clauses

• Clear scope and deliverables: Use a statement of work with outcomes, milestones and acceptance criteria rather than task‑by‑task supervision.
• Genuine substitution: Include a workable substitution clause, with the contractor responsible for vetting and paying any substitute.
• Control and autonomy: Set project deadlines and standards, but avoid directing how, when and where the individual works unless objectively necessary (e.g. security).
• Payment model: Fixed price or milestone‑based models better support outside IR35 than hourly timesheets that mirror employment. Handle expenses carefully.
• Liability and insurances: Require appropriate professional indemnity and public liability cover, with responsibility for rectifying defective work.
• IP and confidentiality: Make sure intellectual property is assigned and confidentiality is protected without creating employment‑style obligations.
• Termination: Avoid open‑ended, indefinite arrangements. Use project‑based terms with clear end dates or deliverables.

If you also work with supply chains, a robust Sub‑Contractor Agreement helps keep terms consistent through the chain.

Your IR35 Process

• Status workflow: Create a simple checklist for managers to trigger a status review before engaging any PSC (personal service company).
• Reasonable care: Document the status analysis, including interviews with the project lead about control, deliverables and working practices.
• SDS and disputes: Issue a written SDS explaining your conclusion and reasons. Set up a fair disagreement process with a named contact and timeframes.
• Onboarding: Train hiring managers not to impose employment‑style processes on contractors (e.g. set working hours, holiday approvals, staff benefits).
• Monitoring: Reassess status if the scope shifts, extensions are agreed, or working practices change.

It’s also sensible to explain to stakeholders the difference between a contractor and an employee, as part of your policies, and when to use an Employment Contract instead of a contractor route.

Who Pays Tax And NICs Under IR35?

Once you’ve made a status determination, who is actually on the hook for PAYE and NICs depends on your supply chain.

• Client = fee‑payer: If you pay the contractor’s company directly, you’re usually the fee‑payer. For inside IR35, run PAYE and employer NICs on the deemed direct payment, and report via RTI.
• Agency in the chain: If you pay an agency, they’re often the fee‑payer and must operate PAYE/NICs where IR35 applies. However, liability can transfer if you fail to take reasonable care or don’t pass on the SDS.
• Debt transfer rules: If HMRC can’t collect from the fee‑payer, liability can move up the chain in cases of non‑compliance. This is why passing on the SDS and doing due diligence on suppliers matters.

Remember that IR35 is about income tax and NICs, not VAT. Even if an assignment is inside IR35 and PAYE is operated, VAT invoicing may still be relevant in the chain. Ensure your finance team understands both pieces.

Common IR35 Scenarios For SMEs

A Developer Through A PSC For A 6‑Month Project

You need a React developer to deliver a discrete module. You engage their company on a fixed‑price statement of work with milestones. They can work remotely, set their hours, and they have a genuine right of substitution. You hold project stand‑ups but don’t direct methods. With the right terms and practices, this can be outside IR35 - provided you’re consistent in reality.

Rolling Extensions That Become “Business As Usual”

A 3‑month assignment gets extended repeatedly, and the contractor is now on daily stand‑ups, managing internal staff and taking part in appraisals. Even if it started outside IR35, the working reality now looks employment‑like. Reassess status; you may need to bring them in on an Employment Contract or redesign the engagement.

Agency And Umbrella Company Supply Chains

Where an agency or umbrella company is involved, check who is the fee‑payer, that the SDS is passed down, and whether the umbrella is operating PAYE correctly. Do basic due diligence - IR35 debt transfer rules can make non‑compliance your problem later.

Short, Outcome‑Based Engagements

A two‑week security audit with a fixed deliverable, conducted independently with the consultant’s tools and methodology, is often a good candidate for outside IR35. Keep it outcome‑focused; avoid imposing set hours or multi‑layer approvals that blur independence.

Contractor Based Overseas

IR35 applies only if the individual performs work in the UK (or is UK tax resident). If you’re engaging overseas contractors who carry out work wholly outside the UK, IR35 typically won’t apply - but other cross‑border tax, IP and data issues will. Get tailored advice before assuming you’re outside scope.

Contractor vs Subcontractor On A Client Project

If you’re leading a client project and want to bring in an independent specialist, be clear on roles. A clean contractor vs subcontractor split, clear deliverables and consistent practices reduce the risk of status drift in either direction.

Practical Compliance Checklist

Here’s a simple, repeatable process you can adapt to your business:

1. Screen the engagement early: Is the work suitable for a contractor? If it’s an ongoing role with set hours and line management, consider hiring as an employee instead.
2. Confirm whether you’re “small”: If you’re small under the Companies Act thresholds, note that the contractor’s PSC is responsible for IR35 - but keep an eye on employment status risks for rights and benefits.
3. Assess status (reasonable care): Speak to the project lead about control, substitution, deliverables, integration and financial risk. Use a structured questionnaire and save notes.
4. Draft the right contract: Put in place a tailored Contractor Agreement (plus statement of work). Align clauses with real‑world working practices to avoid contradictions.
5. Issue a written SDS: If you’re medium/large, provide the contractor and supplier with your SDS and reasons. Set out your disagreement process and contact point.
6. Set up payroll correctly: For inside IR35, make sure the fee‑payer runs PAYE and employer NICs on the deemed payment. Keep VAT handling consistent with the supply chain.
7. Educate managers: Share a one‑page guide on “how to work with contractors” - no holiday approvals, set hours, or employee benefits; focus on deliverables and outcomes.
8. Monitor and re‑check: Review status at extension points, scope changes or where the contractor starts managing internal teams.
9. Tidy your supply chain: If you pass work to a subcontractor, ensure your Sub‑Contractor Agreement mirrors key IR35‑relevant terms (substitution, autonomy, deliverables) and that SDSs flow through where required.
10. Escalate edge cases: If the engagement sits on the borderline, or involves complex chains or cross‑border work, seek targeted legal advice early.

IR35 And Employment Rights: Keep The Concepts Separate

IR35 is a tax framework. Separately, an individual may still argue they are a “worker” or “employee” for employment law rights like holiday pay or minimum wage, regardless of how the tax is handled. This is why status needs careful thought across both regimes.

Make sure your team understands the overlap between employment status tests and IR35, and when to pivot to an Employment Contract because the role is better treated as employment from day one.

How To Reduce IR35 Risk Without Slowing Down Delivery

You still need to deliver projects quickly. The trick is building an IR35 process that’s lightweight but consistent:

• Start with outcomes: Write a crisp statement of work that focuses on deliverables, not tasks. Keep approval points to quality and milestones, not methods.
• Keep contractors distinct: Avoid integrating contractors into employee workflows and benefits. Provide access only to what’s needed to deliver the project.
• Structure payments: Favour milestone or fixed‑price payments where appropriate; reduce day‑rate timesheet culture for outside IR35 engagements.
• Use the right documents: A well‑structured Contractor Agreement with a workable substitution clause, IP assignment and sensible liability provisions helps maintain the right boundaries.
• Train once, reuse often: Give hiring managers a short playbook with examples of outside vs inside IR35 practices and a simple flowchart for status checks.

If this feels daunting, don’t worry - once you’ve set up the building blocks, you’ll have a repeatable way to keep engagements compliant without bottlenecks.

Key Takeaways

• IR35 asks whether, ignoring the contractor’s company, the individual would be your employee for tax - if yes and you’re medium/large, the fee‑payer must run PAYE and employer NICs.
• Check if you’re “small” under the Companies Act thresholds; if you are, the contractor’s PSC decides IR35, but you still need to manage employment status risks.
• Take reasonable care with each engagement: assess control, substitution, mutuality of obligation, integration and financial risk, and record your reasoning.
• Align contracts and reality: use a tailored Contractor Agreement and outcome‑based statements of work. Avoid employment‑style practices for contractors.
• Issue a clear SDS (if required), pass it through the supply chain, and set up PAYE/NICs correctly for inside IR35 engagements to avoid debt transfer risk.
• Reassess status when scope or working practices change, and consider an Employment Contract when the role is ongoing and managed like an employee.
• For cross‑border work, IR35 may not apply, but other rules do - get advice when engaging overseas contractors or complex supply chains.

If you’d like help setting up a compliant process, drafting a robust Contractor Agreement or sense‑checking a tricky status call, our team can guide you. You can reach us on 08081347754 or team@sprintlaw.co.uk for a free, no‑obligations chat.