IR35 Status Determination Disputes: How to Appeal to the Tax Tribunal

Last updated: March 2026

Quick Answer

If HMRC has determined that your engagement falls inside IR35 — meaning you should be treated as an employee for tax purposes — you can challenge that decision. The off-payroll working rules (commonly called IR35) apply to contractors working through intermediaries, typically personal service companies. Since April 2021, medium and large private sector clients have been responsible for making status determinations, but HMRC can investigate and override those determinations. If you disagree with HMRC's conclusion, you can request a review and, if necessary, appeal to the First-tier Tribunal (Tax Chamber). Your appeal bundle must demonstrate the reality of your working arrangements, not just what the contract says.

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What Is IR35 and Why Does It Matter?

IR35 refers to the intermediaries legislation originally introduced by section 60 of the Finance Act 2000 (now Chapter 8 of Part 2 of the Income Tax (Earnings and Pensions) Act 2003). Its purpose is to prevent individuals from avoiding employment taxes by providing their services through an intermediary — usually a personal service company (PSC) — when the reality of the relationship is one of employment.

If IR35 applies, the income paid to the intermediary is treated as employment income, and PAYE and National Insurance contributions must be accounted for. The financial difference between being inside and outside IR35 can be substantial — often tens of thousands of pounds per year.

The Off-Payroll Working Rules (Post-April 2021)

Since April 2021, the responsibility for determining employment status has shifted for engagements with medium and large private sector organisations. Under the current rules:

The rules do not apply to small companies (as defined by the Companies Act 2006). If your client is a small company, the PSC still makes its own determination.

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HMRC's Check Employment Status for Tax (CEST) Tool

HMRC provides a free online tool called CEST (Check Employment Status for Tax) to help determine whether a worker is employed or self-employed for tax purposes. Many end clients use CEST to make their Status Determination Statements.

Limitations of CEST

CEST has been widely criticised by tax professionals, tribunals, and contractors alike. Key criticisms include:

• It does not consider mutuality of obligation — a fundamental factor in employment status case law that CEST simply does not ask about
• Binary questions for nuanced situations — many engagements involve complex, blended working patterns that do not fit neatly into yes/no answers
• Frequent "unable to determine" results — CEST returns an indeterminate result in a significant proportion of cases, leaving the user no better off
• Not binding on the tribunal — HMRC has stated that CEST results are not legally binding, and tribunals have repeatedly departed from CEST outcomes in decided cases
• Inconsistent with case law — several tribunal decisions have found that CEST reached the wrong conclusion on the facts

If HMRC has relied on a CEST determination to conclude that IR35 applies to your engagement, that determination is very much open to challenge.

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The Key Tests for Employment Status

Employment status for IR35 purposes is determined by applying a series of common law tests developed through decades of case law. The leading authorities include Ready Mixed Concrete v Minister of Pensions [1968], Market Investigations v Minister of Social Security [1969], and, more recently, HMRC v Atholl House Productions [2022].

The Three Core Tests

Additional Factors

Beyond the three core tests, the tribunal considers a range of additional factors:

• Financial risk — does the contractor bear genuine financial risk (e.g., fixed-price contracts, liability for defective work, uncapped costs)?
• Provision of equipment — does the contractor provide their own tools, software, and equipment?
• Part and parcel of the organisation — is the contractor integrated into the client's organisation (attending social events, on the intranet, using client email)?
• Business on own account — does the contractor operate a genuine business, with multiple clients, a business website, professional indemnity insurance, and marketing activity?
• Right of termination — can either party terminate on short notice (suggesting employment), or is termination subject to a fixed term or project completion?
• Intention of the parties — while not determinative, the parties' understanding of the relationship is a relevant factor

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Challenging an HMRC IR35 Determination

Step 1: Understand the Determination

HMRC's determination will set out why it considers IR35 applies. It will typically analyse the engagement against the key tests and conclude that, on balance, the hypothetical contract points to employment. Read it carefully and identify the specific points you disagree with.

Step 2: Gather Evidence of the Reality

The single most important thing to understand about IR35 is that the tribunal looks at the reality of the working arrangement, not just the written contract. A contract that says "the contractor may send a substitute" is meaningless if, in practice, you have never sent one and the client would not accept one.

Evidence of reality includes:

• Emails and messages showing how work was allocated, supervised, and reviewed
• Timesheets and invoices showing irregular patterns (suggesting project-based, not employment)
• Evidence of substitution — occasions when you sent or offered a substitute, or the client engaged other contractors
• Evidence of other clients — invoices, contracts, or tax returns showing work for multiple clients
• Evidence of financial risk — fixed-price quotes, liability for defective work, professional indemnity insurance
• Evidence of equipment — receipts for your own laptop, software licences, tools
• Business documentation — business website, marketing materials, Companies House records, VAT registration

Step 3: Request an Internal Review

Write to HMRC within 30 days of the determination and request a review. Set out, in detail, why you believe the determination is wrong, supported by evidence. A different HMRC officer will reconsider the case.

Step 4: Appeal to the Tribunal

If the review upholds the determination, appeal to the First-tier Tribunal (Tax Chamber) within 30 days of the review conclusion letter. There is no filing fee.

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Preparing Your IR35 Appeal Bundle

IR35 appeals are evidence-intensive. The tribunal needs to see the reality of your working arrangement, and that means a comprehensive, well-organised bundle.

Recommended Bundle Structure

Key Principles for IR35 Bundles

1. Focus on reality, not paperwork — the contract matters, but the working reality matters more. Include evidence of what actually happened day-to-day.

2. Address every test — your bundle should contain evidence relevant to personal service, control, mutuality of obligation, financial risk, and the other factors. Do not leave gaps.

3. Include contrary evidence — if there are facts that support HMRC's position (for example, you worked fixed hours at the client's office), include them and address them in your witness statement. The tribunal will respect honesty.

4. Chronological correspondence — arrange emails and letters in date order so the tribunal can follow the story of the engagement.

5. Cross-reference thoroughly — your witness statement should refer to specific page numbers in the bundle. This makes the hearing far more efficient.

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Key IR35 Cases to Know

Understanding recent tribunal decisions helps you frame your appeal. Several landmark cases have shaped the current law:

These cases illustrate that the outcome depends on a holistic assessment of all the factors — no single test is decisive.

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Using BundleCreator for IR35 Appeals

IR35 appeals generate a substantial volume of documents — contracts, emails, invoices, tax returns, insurance certificates, and more. Organising all of this into a paginated, indexed, bookmarked bundle is exactly what BundleCreator is designed to do.

With BundleCreator, you can:

• Upload documents from your engagement — contracts, correspondence, invoices, and evidence of working practices
• Organise them into thematic sections (substitution, control, financial risk, etc.)
• Apply automatic consecutive pagination
• Generate a hyperlinked index and PDF bookmarks
• Ensure the bundle is text-searchable with built-in OCR
• Export a professional, tribunal-ready electronic bundle

For contractors, accountants, and tax advisers dealing with IR35 disputes, BundleCreator takes the administrative burden off your hands so you can focus on building the strongest possible case.

Prepare your IR35 appeal bundle with BundleCreator →

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Frequently Asked Questions

What is a Status Determination Statement (SDS)?

An SDS is the written document that the end client (for medium and large organisations) must issue when determining whether IR35 applies to an engagement. It must set out the reasons for the determination and be communicated to the worker and the fee-payer. If you disagree with the SDS, you have the right to raise a dispute with the client, who must reconsider the determination.

Can I challenge the client's Status Determination Statement?

Yes. You have the right to make representations to the client, who must respond within 45 days. If the client upholds the SDS and you still disagree, HMRC's investigation or a tribunal appeal may be the next step. The client's determination is not final — it can be overridden by HMRC or by the tribunal.

Does CEST determine my status?

No. CEST is a tool, not a legal authority. The tribunal is not bound by CEST results and has frequently departed from them. If HMRC relies on CEST to support its determination, you can challenge the tool's analysis and present your own evidence of the working reality.

What if I have already paid the tax demanded by HMRC?

Paying the tax does not prevent you from appealing. You can appeal and, if successful, claim a refund of the tax paid. In some cases, the tribunal may stay the collection of tax pending the outcome of the appeal, though this is not automatic.

How long do IR35 tribunal appeals take?

From lodging the appeal to receiving a decision, IR35 cases typically take 12 to 24 months, depending on complexity and tribunal listing capacity. Complex cases with multiple engagements or novel legal arguments may take longer.

Can HMRC investigate past years?

Yes. HMRC can open enquiries into past years, subject to statutory time limits. For non-deliberate errors, the limit is generally 4 years. For careless errors, it is 6 years. For deliberate errors, the limit extends to 20 years. IR35 investigations can therefore cover multiple tax years.

What are the financial consequences if IR35 applies?

If IR35 applies, the income from the engagement is treated as employment income. This means:

• Income tax at your marginal rate on the deemed employment income
• Employee NICs on the deemed employment income
• Employer NICs payable by the fee-payer (or, in some cases, the PSC)
• Interest on the unpaid tax from the original due date
• Penalties if HMRC considers the failure to apply IR35 was careless or deliberate

The combined effect can be a significant additional tax liability, sometimes running to tens of thousands of pounds across multiple tax years.

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This article is provided for general informational purposes only and does not constitute legal or tax advice. The law and procedure described applies to England and Wales. If you are unsure about your specific situation, seek independent legal or professional advice.