IR35 is a word used to describe two sets of tax legislation that are designed to combat tax avoidance by workers, and the firms hiring them, who are supplying their services to clients via an intermediary, such as a limited company, but who would be an employee if the intermediary was not used.
Such workers are called ‘deemed employees’ by Her Majesty’s Revenue and Customs (HMRC). If caught by IR35, they have to pay income tax and National Insurance Contributions (NICs) as if they were employed. The financial impact of IR35 is significant. It can reduce the worker’s net income by up to 25%, costing the typical limited company contractor thousands of pounds in additional income tax and NICs.