No. In your company calendar, you can add a new client when booking their first appointment by selecting the desired time of the appointment and then ‘Add a Client’.

Alternatively, go to the ‘Clients’ tab and select ‘Add a Client’. 

If a client wants to become an online user, point them to https://book.Click4Time.com and follow the 'New User' registration link.

Clients can also choose to book appointments online as a ‘Guest’ and bypass the online user registration.  Clients choosing to book as a Guest will not have access to personal calendar syncing, appointment management, invoice printing or testimonial submissions.  If you want to disable Guest booking and force clients to register or log in, go to Settings / Configuration / Advanced / Client Booking Limits and set ‘Clients Must Login to Create Appts’ to ‘Yes’.