IR35 and Off-Payroll Working: The Complete UK Contractor's Guide to Status and Compliance

IR35 and Off-Payroll Working: A Plain-English Guide for UK Contractors

IR35—formally called the "Intermediaries Legislation"—is one of the most misunderstood areas of UK tax law. If you work as a contractor through your own limited company, supply services to a client, and might otherwise be an employee, IR35 could apply to you. The consequences of getting it wrong are serious: unpaid tax liabilities, National Insurance arrears, and potential penalties.

This guide explains what IR35 is, who it affects, how to determine your status, and what compliance looks like in practice.

What Is IR35?

IR35 is a UK tax rule designed to prevent tax avoidance by workers who would be employees if they were engaged directly, but who instead work through an intermediary (usually a personal services company or PSC—a limited company set up by the individual).

In simple terms: if you work like an employee (same client, set hours, control over how you work, no genuine business risk), but invoice through a company to avoid employment taxes, IR35 can "pierce the veil" and treat you as an employee for tax purposes, even though you're legally self-employed.

When IR35 applies, you must pay income tax and National Insurance contributions (both employee and employer portions) on the income, as if you were a traditional employee—though you still retain the structure of a limited company.

Key Official Source

The HMRC IR35 guidance is the authoritative starting point for understanding the rules and how HMRC assesses status.

Who Does IR35 Affect?

IR35 typically applies to:

• Freelancers and contractors working through a personal services company (PSC) or limited company.
• Workers in professional services (IT, engineering, management consulting, recruitment, accountancy).
• Individuals with a single or dominant client who retains significant control over how the work is done.
• Contractors who work on-site at a client's premises, often on a full-time or near-full-time basis.

IR35 does not apply to:

• Genuine small businesses with multiple clients, significant overheads, and real business risk.
• True freelancers and suppliers who maintain control over their work and have genuine independence.
• Employees directly employed—they're already in PAYE.

The Critical Test: Employment Status

HMRC uses a multi-factor analysis to determine whether a working relationship would be a contract of employment "if the intermediary were removed." There is no single definitive test, but HMRC examines:

Control

Does the client (or an agent) dictate how, when, and where the work is done? If you must follow specific instructions, attend set meetings, and work set hours, that points toward employment.

Mutual Obligation

Is there a genuine obligation for the client to offer work, and for you to accept it? Or can either party walk away freely? Real employment typically has mutual obligation; genuine freelancing does not.

Financial Risk

Do you bear a genuine risk of loss? Can you incur expenses that won't be reimbursed? Can you make a profit or loss on the contract? Employees typically don't bear real financial risk; self-employed people do.

Integration

Are you integrated into the client's business—treated as part of the team, using their tools and systems, following their policies? Or are you clearly separate and independent?

Substitution

Can you send a substitute to do the work if you're unavailable? If the contract is personal to you and substitution isn't allowed, it suggests employment.

Provision of Equipment

Do you use your own tools and technology, or does the client provide everything? Self-employed contractors typically bring their own resources.

For a detailed walkthrough, HMRC's employment status indicator tool and their decision tree for contracts for services can help, though they are guides only and not conclusive.

Off-Payroll Working Rules (2021 Onwards)

In April 2021, the off-payroll working rules changed significantly. If you're a contractor in the private sector:

• The responsibility for determining IR35 status shifted from the contractor to the engager (the client or the agency hiring you). Historically, contractors assessed their own status; now, the client or hiring agency must decide.
• If the client/agency decides IR35 applies, they must operate PAYE on the payments to your PSC (or deduct the equivalent tax and National Insurance directly).
• You, as the contractor, can still challenge the determination if you believe it's wrong, but the burden initially rests with the engager.
• The rules apply in the private sector. The public sector has had similar rules since 2017, where the public employer bears the responsibility.

This shift in responsibility has made it critical for contractors to communicate clearly with clients about status before engagement begins.

How to Determine Your IR35 Status

1. Conduct an Honest Self-Assessment

Review your engagement against the factors above (control, risk, integration, etc.). Be honest: do you genuinely function as an independent business, or as a quasi-employee?

2. Use HMRC's Tools

HMRC's employment status indicator and decision trees provide a framework, though HMRC notes these are non-binding guides.

3. Seek Professional Advice

Status determinations are fact-specific and often ambiguous. A qualified accountant or tax advisor should review your contract and working arrangement. Many borderline cases benefit from a formal advice letter that you can share with your client.

4. Consider a Formal Status Determination

If there's genuine uncertainty, you or your client can ask HMRC for a formal determination under the Advance Clearance procedure. This takes time but provides certainty.

What Happens If IR35 Applies?

If IR35 is determined to apply to your engagement:

• The client or agency must deduct income tax and National Insurance (both employee and employer portions, often called "Deemed Employment Income" or DEI) from the fees paid to your PSC.
• You (or your accountant) will need to file a Self-Assessment return including the deemed employment income, and reconcile it with any PAYE paid.
• You cannot claim expenses against the deemed employment income in the same way a genuinely self-employed person can; allowable deductions are limited.
• Your company may still have corporation tax obligations on any retained profits.

The practical effect is that you'll pay significantly more tax and National Insurance than a true self-employed contractor, but typically less than a directly employed employee (because you can structure dividends and salary to some degree).

Compliance and Record-Keeping

Whether or not IR35 applies, maintain clear records:

• A copy of your contract with the client, clearly setting out terms of engagement, liability for expenses, termination, and rights of substitution.
• Evidence of your independent business, such as marketing materials, multiple client contracts (if applicable), and business expenses.
• Timesheets or records of work done, including dates and scope.
• Communications with the client or agency about your status determination and any IR35 decision.
• Annual accounts and payroll records for your PSC, signed off by a licensed accountant.

If HMRC investigates, these records will help demonstrate whether IR35 actually applies.

Common Myths and Clarifications

"If I invoice weekly, I'm self-employed."

No. Billing frequency is only one factor and is easily overridden by control, lack of risk, and integration. Many employees are paid weekly; many genuinely self-employed people bill weekly too.

"If I've been trading for 5+ years without challenge, IR35 doesn't apply."

Not necessarily. HMRC can go back and reassess status retroactively (usually up to 4 years, or longer if there is deliberate avoidance). The absence of a prior challenge doesn't confirm status.

"My accountant says I'm fine."

Get it in writing. An accountant's informal reassurance is not the same as a professional determination. If HMRC disagrees, you need evidence that you took reasonable care to comply.

"All contractors in my sector are unaffected by IR35."

Not true. Each engagement is assessed on its facts. Two contractors in IT might reach different conclusions based on their respective working arrangements.

Key Steps to Take Now

1. Review your contract(s) with your client(s) and assess honestly against the employment status factors.

2. Discuss your status with your client or hiring agency before engagement—clarity upfront prevents disputes.

3. Engage a qualified accountant to review your arrangement and advise on IR35 risk.

4. Document your independent business status through contracts, marketing, multiple clients (if applicable), and business records.

5. Keep meticulous records of hours, scope, client communications, and invoices.

6. Review your status annually, especially if your working arrangement changes.

If you are operating under IR35 but had not previously accounted for it, contact a tax professional urgently to discuss a potential Voluntary Disclosure with HMRC.

Professional Guidance Is Essential

IR35 is complex, and the consequences of non-compliance are real. HMRC has invested significantly in IR35 enforcement, and the number of successful assessments is rising. Every engagement is unique, and what applies to one contractor will not apply to another.

At Next Tax Source, our chartered accountants and tax specialists review IR35 status for contractors across the UK, the US, and the UAE. We help you understand whether your arrangement is caught, what compliance looks like, and how to structure your engagement and company finances to minimize tax fairly and legally.

If you'd like a confidential assessment of your status or advice on compliance, book a consultation or visit our pricing page to see how we can help.

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FAQs

Q: Can I appeal if my client says IR35 applies and I disagree?

A: Yes. You have the right to challenge your client's determination. You can ask HMRC for a formal status ruling or raise a dispute during Self-Assessment. A professional advisor can represent your position and gather evidence to support your case.

Q: What if I work for multiple clients?

A: Multiple clients generally point away from IR35, because it suggests you're running a genuine business with varied income sources. However, if one client dominates your time and income, IR35 may still apply to that engagement. Each client relationship is assessed separately.

Q: Do I need a limited company, or can I be a sole trader and avoid IR35?

A: IR35 applies specifically to intermediaries (companies). Sole traders are not caught by IR35 because there's no intermediary to pierce. However, HMRC may assess a sole trader as having employment status in the same way, so it's not a complete loophole. The key is genuine independence, not the legal structure.

Q: How much extra tax and National Insurance will I pay if IR35 applies?

A: This depends on your income, location, and other factors. Broadly, if IR35 applies, you'll pay employer's National Insurance (currently around 15%) plus income tax and employee's National Insurance on the deemed employment income. We recommend a full tax plan with a qualified accountant to model the actual liability for your circumstances.

Q: What records should I keep to prove I'm genuinely self-employed?

A: Keep your contract, evidence of multiple clients (if applicable), business marketing materials, records of business expenses, invoices, timesheets, and any communications with your client about your independent status. If challenged, HMRC will review these to determine whether the working relationship would constitute employment.

Frequently asked questions

Can I appeal if my client says IR35 applies and I disagree?

Yes. You can challenge your client's determination by requesting a formal HMRC status ruling or raising a dispute during Self-Assessment. A professional tax advisor can help gather evidence and represent your position.

What if I work for multiple clients?

Multiple clients generally point away from IR35 and suggest you run a genuine business. However, if one client dominates your time and income, IR35 may still apply to that specific engagement. Each client relationship is assessed separately.

Do I need a limited company, or can I be a sole trader to avoid IR35?

IR35 applies to intermediaries (companies), not sole traders. However, sole traders can still be assessed as employees under general employment law. Genuine independence—not just legal structure—is the key.

How much extra tax will I pay if IR35 applies?

You'll typically pay employer's National Insurance (around 15%) plus income and employee's National Insurance on the deemed employment income. A qualified accountant should model your actual liability based on your income and circumstances.

What records should I keep to prove I'm genuinely self-employed?

Keep your contract, evidence of multiple clients (if applicable), business materials, expense records, invoices, timesheets, and communications about your independent status. These help defend your position if HMRC investigates.