Most contractor guidance on IR35 leads with the right of substitution, whether a contractor can send someone else to do the work instead of turning up personally. It’s the easiest test to explain, so it gets the most airtime. It’s also not the one that tends to decide these cases in practice. Control is.
Control asks a narrower question than most contracts address: not just who does the work, but who directs how, when and where it gets done. If the client tells a contractor which hours to work, supplies the equipment, and manages the day-to-day method of the work rather than just the outcome, that starts to look like employment, regardless of what the contract calls the relationship.
This was one of the central points in HMRC v Atholl House Productions Ltd [2022] EWCA Civ 501, the Kaye Adams case and the first IR35 dispute to reach the Court of Appeal. The court confirmed that control and mutuality of obligation are preconditions for employment status, but not proof of it on their own. IR35 status is decided on a multi-factorial basis, looking at everything reasonably available to both sides, not ticking one box and stopping.
Most standard contractor agreements handle substitution reasonably well, because it’s easy to write a clause about. Control gets far less attention, and it’s usually the weaker link. A contract can say the contractor works independently, but if the client provides a laptop, sets fixed hours, and specifies the exact method rather than just the deliverable, the written contract won’t save the position if it doesn’t match reality.
The fix is to make sure the contract’s control clauses reflect how the engagement actually runs, not how it would look best on paper. That means being specific about who supplies equipment, confirming the contractor decides their own working method and hours where genuinely possible, and avoiding language that implies day-to-day supervision.
Most people don’t realise HMRC and the tribunals weigh actual working practice more heavily than the wording of the contract itself. A perfectly drafted substitution clause means very little if the contractor’s laptop, hours and instructions all come from the client.
For businesses engaging contractors across Cardiff and the wider Cardiff Capital Region, this is worth checking now rather than waiting for a status review. Look at who actually controls the how, not just the what, and make sure the contract and the reality match.
Irfan Dadabhai is the founder of LexPact (lexpact.co.uk), an AI contract platform that generates UK IR35-compliant contractor agreements, NDAs and Terms of Business built around the statutes and case law that actually apply to them.