IR35 is anti-avoidance legislation intended to stop a taxpayer from gaining a financial advantage by using a limited company compared with being an employee. It can catch people who might otherwise have expected to be considered self-employed if they hadn’t used a company.
IR35 will only take effect where there is an intermediary company (or partnership) between the person doing the work and the practice – so it is not relevant for a self-employed GP carrying out sessional GP locum work directly for a practice.
Up until April 2021, where the ‘end user’ (the practice) was a public sector employer (which a general practice is deemed to be), it was the responsibility of the practice to make the decision whether or not IR35 should apply.