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 investigation insured membership
  • 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
  • FREE result in 15 minutes
  • Prove your status with a report and certificate starting from just £49.99
  • Tax investigation insured Membership only £199.99

Accountancy firm

  • 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
  • IR35 Volume Audit: test all your contractors in a single day!


  • 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 19 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

Renoir, the IR35 AI lawyer

Our solution features Renoir, our AI-powered virtual employment lawyer, and a key component of your IR35 compliance process.

Renoir’s AI capabilities enable him to carefully evaluate the contextual importance of each factor impacting IR35 status, as required by employment case law.

Without Renoir, an employment status lawyer will charge you for 2-3 hours’ work, and turnaround time may take a week. Renoir delivers a free comprehensive assessment within 15 minutes.

Renoir is self-learning, continually collating market data and trends. Having Renoir on your team also provides big data insights from the thousands of tests conducted each month, helping you to better manage IR35 risk.

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

Find out more about Renoir

Who are we?

IR35 Testing

19 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

IR35 Ribbon Trusted by over 100,000 contractors

  • Taxation
  • BBC Radio 4
  • Financial Times
  • The Register
  • Lawyer Monthly
  • Personnel Today
  • Recruiter
  • Taxation Web
  • Yahoo Finance
  • Accounting Web
  • Management Today
  • The Mail Online
  • The Telegraph
  • The Guardian

ContractorCalculator and IR35Testing in the media