A CF30 is not a certification per se. It is part of the term used by the Financial Conduct Authority when referring to ‘controlled functions’.
The CF30 is essentially the FCA controlled function for those dealing directly with end clients, normally advising or similar, for those reading this who are not aware. There are other controlled functions such as the directors of the firm, head of compliance, anti money laundering officer, etc.
There is no exam but they would normally expect you to demonstrate to the regulator relevant experience and appropriate qualifications. It is tied to the company that you are employed by so normally the company will want to apply for it on your behalf.
Once you have held a controlled function is is much easier to do it next time around as long as you were not struck off for any reason you just go and do it again somewhere else.
Read FCA’s controlled functions for more details.