The right of substitution is one of the three fundamental tests for determining employment status. If you have a genuine, unrestricted right to send a substitute to perform the work in your place, this is a strong indicator that you are not an employee and your engagement falls outside IR35.
What makes a substitution clause genuine?
A substitution clause in your contract must reflect a real, practical right that could be exercised, not just a theoretical provision. Tribunals look for several factors: the substitute must be someone you choose and engage, not someone the client selects; you must pay the substitute from your own funds; the client can only reject a substitute on reasonable grounds (such as insufficient qualifications); and the right must be unfettered, meaning you can exercise it at any time without needing the client's prior approval.
Exercising substitution in practice
A substitution clause that has actually been exercised carries the most weight. If you have ever sent a substitute to perform work on a client engagement, document it. Even if you have not exercised the right, maintaining a network of contacts who could substitute for you, and being able to demonstrate this to an IR35 assessor, strengthens your position.
Common pitfalls
A substitution clause that requires the client's prior written consent for any substitute effectively negates the right, as it gives the client a veto. Similarly, if the client insists on specific individuals and would not accept anyone else, the right is not genuine. Clauses that only allow substitution in cases of illness or holiday are too narrow to indicate genuine self-employment.
Practical advice
Ensure your contract includes a robust substitution clause drafted or reviewed by an IR35 specialist. Beyond the contractual provision, take practical steps to make the right exercisable: identify potential substitutes, confirm their availability and rates, and keep records. If you do use a substitute, even for a single day, document the entire process.