The ultimate IR35 compliance solution

We are the most comprehensive IR35 compliance solution available to hirers, agencies, accountants, service providers and contractors. We deliver fast and accurate artificial intelligence (AI) driven online assessments, with access to an extensive range of IR35 support services, for complete protection in one place.

  • Contractors – achieve IR35-free contracting with minimum hassle
  • Agencies, accountants and hirers – minimise risk and admin compliance overheads
  • Service providers – Sell solutions to thousands of contractors

Who are you?


  • Get and stay outside IR35
  • Achieve tax savings worth thousands
  • Take the test in 15 minutes
  • Prove your status with a report and certificate


  • Ensure your contractors are tested for IR35
  • Reduce your risk and compliance costs
  • Demonstrate due diligence to HMRC
  • Deliver added value services at no extra cost


  • Sell IR35 reviews, consultative services and tax insurance
  • Boost revenues and grow your client base
  • Sell directly to contractors
  • Gain additional promotion via our PSL

Our IR35 assurance process

IR35 Testing Flowchart

IR35 Testing:

  • Helps contractors stay outside IR35
  • Keeps agencies tax compliant
  • Minimises compliance risk
  • Reduces HMRC investigation costs
  • Includes insurance options for peace of mind

Key features of our IR35 test:

  • Built in 2009, used by over 100,000 contractors
  • Developed by IT, IR35 and employment law experts
  • Encompasses 17 years of IR35 knowledge
  • Delivers IR35 pass certificate
  • Provides expert advice to avoid IR35
  • 28 page IR35 Test Report - click to see sample

The benefits of an AI-powered solution

Our solution features Renoir, the name we have given to our AI-powered virtual employment lawyer, and a key component of your IR35 compliance process.

Renoir’s AI capabilities enable him to take a holistic view of each contractor’s working arrangement. This means carefully evaluating the contextual importance of each factor impacting IR35 status, as required by employment case law.

Without Renoir, to achieve an equally accurate evaluation you would have to engage an employment status lawyer - most will likely charge you for 2-3 hours’ work, and may not be able to deliver your result for a week.

In contrast, Renoir delivers a comprehensive assessment within a second of receiving the contractor’s questionnaire responses, potentially cutting turnaround time from 5 days to 15 minutes.

On top of this, Renoir’s self-learning AI means he is able to teach himself about different contexts based on test responses. By identifying outliers and changes to answers over time, Renoir increases the scope for analysis whilst continuing to adapt to the current state of knowledge.

Having Renoir on your team also provides big data insights. Capitalising on the thousands of tests conducted by Renoir each month, your team can identify patterns and trends, and compare benchmarks and contractor test results, helping you to better manage IR35 risk.

With Renoir you’re better informed and more effectively protected against IR35.

Find out more

Who are we?

IR35 Testing

17 years of serving the UK’s contracting community

IR35 Testing is brought to you by ContractorCalculator, the UK’s leading contractor brand and website for contingent workers, with circa 150,000 visitors per month.

Originally created in 1999 to help contractors navigate IR35, ContractorCalculator has evolved into a vital resource hub, offering a range of free online financial and tax calculators, as well as expert commentary from industry leaders.

We also publish the contracting industry Bible, the Contractors’ Handbook, and offer financial services to contractors via ccFinancials.

More about us