It is a requirement of most professional therapy associations, including those that accredit our course, that new therapists undertake supervision. See an article explaining what this means here.
For example, hypnotherapists registered with the G.H.R. are required to engage in this beneficial process for a minimum of 2 hours in any 3 month period during their first 2 years of practice after qualification. They are encouraged to continue this practice after that time.