How it works

Your complete IR35 management solution

IR35 Testing combines a freely accessible artificial intelligence (AI) powered IR35 compliance test with unique access to a range of IR35 experts and tax insurers. It offers all-encompassing protection, whether you’re an agency, service provider, hirer or contractor.

What makes our solution the most accurate IR35 test available?

  • Developed with 19 years' practical experience of IR35
  • Built by industry-leading experts who have consulted with the Treasury on IR35
  • Used by over 100,000 contractors since 2009
  • Uses highly complex weight-based algorithms fine-tuned over many years analysis of IR35 cases
  • Our AI engine, Renoir, underpins the tool’s accuracy, consistency and eliminates bias
  • Big data enables users to accurately benchmark a contractor’s test report against their sector

How the IR35 test works

Our test uses 101 questions to build a comprehensive understanding of the contractor’s relationship with their client.

The answers are analysed using a bespoke algorithm. This is regularly refined in line with the latest IR35 tribunal case outcomes. All algorithmic refinements are subsequently regression tested for robustness against our extensive database of tests conducted.

Our solution’s AI is designed to take the holistic approach a tribunal judge would when determining employment status. The AI also harnesses big data, enabling organisations to compare their contractor’s test results against the several thousand test results delivered by Renoir to date.

All contractors who take the test can purchase a comprehensive and uniquely numbered test report detailing factors impacting their status. Contractors who pass also receive a certificate and client-sign-off page, which can be used to demonstrate due diligence and strengthen any future IR35 defence.

Contractors, agencies/hirers and service providers then have the option to acquire further protection by approaching our approved insurance providers to underwrite any risk.

Who passes the IR35 test?

Contrary to what HMRC would have you believe, the complexity of employment case law means it’s impossible to build a test that provides every single contractor a simple binary yes/no answer.

Nobody can definitively know the IR35 status of a contractor unless it is tested in court.

Whilst there are some factors that will indicate definite fails and definite passes, most evaluations will fall somewhere within the spectrum between the two.

This is how our test works, and it provides the most accurate assessment available, allowing you to use it with confidence.

Results from over 100,000 users so far indicate that 30% of contractors pass, 25% receive a borderline result. 14% are borderline fail, and 30% fail.

IR35 Test Certificate

How the IR35 review process works

Seeking professional assistance can be of great benefit to a contractor who doesn’t achieve a pass result. Depending on the expert’s verdict, there are several potential outcomes:

Contractor is inside IR35

  • Contractor finds out the reasons for the inside IR35 assessment
  • Contractor can consider increasing their rate to mitigate the tax loss from IR35
  • Contractor can decline the contract

Contractor is outside IR35

  • We can add supplementary information to their report, based on the expert’s input, to be included in the pass certificate
IR35 Testing Flowchart

Eliminate all risk with IR35 Protect

Whether you’re a public sector agency or a private sector contractor, you can have access to a range of insurance options to provide further peace of mind for your company.

Use the IR35 report to prove your status to our recommended providers to purchase tax investigation insurance or the more comprehensive tax liability insurance. This includes:

  • A rigorous tax defence from any potential HMRC investigation
  • Full cover against a negative judgment, including tax loss and penalties
  • Absolute peace of mind for your business
over 25,000 passes

Used by over 100,000 contractors

over 20 years

Over 20 years software development experience

since 2009

Built in 2009 and continuosly refined to align with latest IR35 legislation


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