Hello. I complete occasional consultancy work for a small business for which I'm paid hourly/daily. I do not produce anything but share knowledge and advice. Work can be at their office or from my home. I am registered for SA and have earned around £4000. I understand there will be no tax or NI due, however do I need to register as a Sole Trader while completing this work? I am not working with any other companies and do not have any other work. Any advice would be gratefully received. Thank you.