Ushi

I'm interested to here how a sole trader can be deemed to come under IR35 and then be told they have to be taxed at source by the company and then pay Class 1 contributions. I have been through the Manual and followed the thread for sole traders which is no easy task however, as a professional I cannot find anything that says about the number of days you are allowed to do for 1 employer, the length of service being an issue since it can only be taken from the 6th April 2021. So please has anyone got any information on what criteria you would have to meet to come under this rule.