IR35 or off-payroll working rules is a tax law which was introduced by HMRC to combat tax avoidance by people who supply their services through an intermediary (such as a personal services company) who would otherwise be an employee. If the work is inside IR35 then HMRC will expect the correct employment taxes and National Insurance to be paid. If you work through an intermediary which provides your services to an end user organisation in the private and third sectors under a contract for services, that intermediary (which could be your own company) is responsible for assessing your  employment status for tax purposes. If you would be an employee of the end user organisation for tax purposes if it were not for the intermediary, then HMRC will say that you are in deemed employment and PAYE and NICs must be deducted at source by the intermediary. Public sector organisations which contract with intermediaries for the services of individuals are responsible for this employment status assessment and for making deductions at source before making payment to the intermediary. See: Private sector off-payroll working for intermediaries Check your employment status for tax purposes Employment Rights of Workers and Employees How to work out if you are an employee or self-employed