The ultimate IR35 compliance solution

The industry leading IR35 compliance solution for contractors, agencies, accountants and service providers.

Delivering fast, accurate, AI driven online assessments, with access to an extensive range of IR35 support services, for complete protection in one place.

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Tolleys Taxation 2019 Awards finalist
Computing Digital Technology Leaders 2019 Awards finalist

Hirers, agencies and accountancy firms

  • Ensure your contractors are tested for IR35
  • Demonstrate due diligence to HMRC
  • Minimise risk and admin compliance overheads.
  • Offer an outsourced IR35 testing service for your clients
  • IR35 Volume Audit: test thousands of contractors in a single day!
IR35 Shield Enterprise logo


  • Quickly assess and prove your IR35 status
  • FREE result in 15 minutes
  • Report and certificate from just £59.99
  • Tax investigation insured Membership only £199.99

Learn more about IR35 Shield

Our IR35 assurance process


  • Quickly conducts accurate IR35 assessments
  • Keeps agencies tax compliant
  • Minimises compliance risk
  • Provides comprehensive due diligence
  • Includes insurance options for peace of mind

Key features:

  • 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
  • 28 page IR35 Test Report - see sample

The benefits of an AI-powered solution


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.

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
Renoir, the IR35 AI lawyer

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 200,000 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
Contractor Calculator logo

Trusted by over 100,000 contractors

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

ContractorCalculator and IR35Testing in the media