Glossary
Right of substitution
The right to send a qualified replacement to do the work — strong evidence of being outside IR35.
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A genuine right of substitution means you can send another qualified person from your business to perform the work, paid by you, without needing to ask the client.
Tribunals consider substitution one of the strongest indicators of self-employment. An "unfettered" right (no client approval needed) is the strongest version. A "fettered" right (client must approve) is weaker.
The right exists in the contract or in practice — but it has to be real. A clause that's never been used or that the client wouldn't actually allow won't protect you.
Related terms
- IR35 — The UK's off-payroll working rules — they decide whether a contractor should be taxed as a deemed employee.
- Outside IR35 — An engagement that doesn't fall within IR35 — the contractor can use Ltd company tax efficiency.
- Mutuality of obligation (MOO) — An employment-style commitment: the client must offer work, and you must accept it.
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