IR35 by the Numbers: The Facts and Figures Behind It
IR35 Quick Facts
- Introduced: April 2000
- Years in force: Over 25 years
- Major reforms: 2017 (Public Sector), 2021 (Private Sector)
- HMRC estimated tax at risk: Around £1.3 billion per year
- Small private companies continue to decide IR35 status themselves.
- Medium & large organisations are responsible for determining contractor status.
IR35 at a Glance
IR35 is one of the most significant pieces of tax legislation affecting the UK’s flexible workforce. Introduced to tackle ‘disguised employment’, the rules ensure that individuals working like employees pay broadly the same tax and National Insurance as permanent staff. Although originally affecting only contractors operating through their own limited companies, responsibility for deciding employment status has shifted considerably over the years. Today, IR35 impacts contractors, recruitment agencies, consultancies and thousands of private and public sector organisations.
Timeline of IR35
| Year | Milestone | Why It Matters |
| 2000 | IR35 introduced | Contractors became responsible for assessing their own status. |
| 2017 | Public sector reforms | Public authorities assumed responsibility for status decisions. |
| 2021 | Private sector reforms | Medium and large businesses became responsible for determining IR35 status. |
| Today | Ongoing case law | Employment status continues to evolve through tribunal decisions. |
Key Statistic
IR35 has now been affecting the UK’s contractor market for more than 25 years.
How Many People Are Affected?
The UK has over 4 million self-employed workers with IR35 impacting an estimated 250,000 to 300,000 limited company contractors (Personal Service Companies). While hard figures vary, HMRC estimates previous off-payroll reforms have shifted up to 150,000 contractors out of Personal Service Companies (PSCs) and onto standard payroll.
| Sector | Typical Exposure |
| IT & Technology | Very High |
| Engineering | High |
| Project Management | High |
| Financial Services | High |
| Business Consultancy | High |
| Oil & Gas | Moderate to High |
| Healthcare | Moderate |
The Revenue HMRC Is Protecting
HMRC forecast that non-compliance with the off-payroll rules would cost the Exchequer approximately £1.3 billion annually by 2023/24 if the rules were left unchanged.
| Objective | Purpose |
| Reduce tax avoidance | Ensure workers pay the correct tax |
| Increase compliance | Improve consistency of status decisions |
| Protect tax revenues | Recover billions in unpaid tax over time |
HMRC Investigations Continue
IR35 remains one of HMRC’s most actively enforced compliance areas. Published settlements in some cases have exceeded £10 million. IR35 Insurance protects contractors against the costs of defending an HMRC investiation as well as the IR35 tax liabilities, interest and penalties, and for the whole IR35 supply chain.
The Changing Use of CEST
Although millions of determinations have been completed since CEST launched in 2017, publicly available figures indicate usage has declined significantly, with many organisations opting for specialist assessment platforms offering stronger evidence and audit trails, such as The Contractor Compliance Portal.
What Can an Incorrect IR35 Decision Cost?
| Financial Exposure | Applies |
| Income Tax arrears | Yes |
| Employee NIC | Yes |
| Employer NIC | Yes |
| Interest | Yes |
| HMRC penalties | Yes |
| Apprenticeship Levy (where applicable) | Yes |
Why Accurate Assessments Matter
| Key Status Indicator | Why It Matters |
| Control | Who decides how, when and where work is completed? |
| Right of Substitution | Can another suitably qualified person perform the work? |
| Mutuality of Obligation | Is there an ongoing obligation to provide and accept work? |
| Financial Risk | Does the contractor bear genuine commercial risk? |
| Business on Own Account | Does the contractor operate as an independent business? |
| Integration | Is the contractor part of the client’s organisation? |
The Bottom Line
After more than 25 years, IR35 continues to influence how organisations engage contractors. With billions of pounds in tax revenue at stake and ongoing HMRC scrutiny, robust, evidence-based status assessments remain essential for contractors, agencies and end clients.
