Self employed or employed?

My friend is a sole trader but now only works with one client, is paid monthly via invoice and completes a self assessment return. Having look at CEST it now seems they would be classed as employed for tax purposes? What do they do now? Does their client need to do anything? The client has an accountant but my friend doesn't. Wouldn't they know if my friend should be employed or self employed? They don't have a contract in place, just a verbal agreement so I can't check the t's and c's. Not sure what they need to do?

Hi ,
 

Unfortunately, it is not possible to review personal matters in this forum.  For individualised assistance please contact our self assessment helpline or contact our webchat:  Self Assessment: general enquiries   . Thank you .