The level of control exercised by the client over the services which are to be provided, as well as how they are provided, when they are provided, and where they are provided is highly important for determining IR35 status.
It is acceptable for a contractor to mutually agree to execute a particular task at a specific time and place with the client, but he should not be subject to any control or supervision from the client; it should be clear that the contractor is able to execute the work according to how they decide. Alternatively, an employee will probably be told where and when the services should be delivered; this is shown in the case of Morren v Swinton and Pendlebury Borough Council (1965).
Having said this, for control to be relevant, it needs to be a lot more than just shallow monitoring or reviewing of outputs. Except for when a contractor is “tied hand and foot” to the client, then the detrimental level of control is not present. [Chaplin v Australian Mutual Provident]