Personal service
[ch 2: pages 36-37]A key requirement of both “employee” and “worker” status is a legal obligation to carry out work personally. Someone who has a genuine, unrestricted right to send a replacement of their choice to do their work will be self-employed (Pimlico Plumbers v Smith [2018] UKSC 29). As long as the contractual right to send a substitute is real and unrestricted, it does not matter whether it is ever used (Autoclenz v Belcher [2011] ICR 1157).
If a contract permits a substitute but only with the employer’s approval, there is no unrestricted right to send a replacement and the individual is probably a worker (Byrne Brothers (Formwork) Ltd v Baird and others [2002] IRLR 96).
Someone can be a worker if their contract allows them to delegate duties to someone else when they are unable to carry them out (for example, while on holiday or ill). However, a contract term that genuinely allows someone to send a substitute of their choice simply because they are unwilling to carry out their work is inconsistent with worker status (James v Redcats [2007] IRLR 296).
Substitution clauses have been used to deny the lowest paid and most insecure workers access to basic worker rights. See page 39: Challenging false self-employment.