Supervision, Direction and Control
For a worker to be treated as a CIS Subcontractor for tax purposes, you as the contractor must ensure they are not subject to your supervision, direction, or control (SDC).
If a worker is subject to SDC, HMRC will likely view them as an employee. This doesn’t just affect the worker’s ability to claim expenses — it can also create liabilities for you, such as Employers’ National Insurance and the obligation to deduct PAYE.