This will depend on your situation. The main thing is that all installations designed from January 2019 onwards must comply with the new regs. As such if you are happy with your understanding of the new Blue book then there is no need to take a course. However if you belong to scheme such as the NICEIC, ELECSA, STROMA, Napit or others then they will tell you when you need to complete the qualification by. If you are registered with the JIB ECS check system then you will also need to achieve the latest qualification by a date which they will confirm to you.