A Student's Paying Client is the main Client who is primarily responsible for paying Invoices or Credit Requests for Lessons a Student has taken or will take. Every Student must have one. You can see a Student's Paying Client via People > Students > select the Student.
A Student can also have other Clients attached to their profile who are not responsible for payment. You can read about Associated Clients here.
Changing the Paying Client
If there are no paid or outstanding Invoices associated with any Lessons a Student has taken, you can change a Student's Paying Client via People > Students > select the Student > Actions > Edit Profile, then adjusting the 'Paying Client' field using the dropdown menu.
Changing a Student's Paying Client.
Note: If there are paid or outstanding Invoices associated with the Student, you will not be able to change the Student's Paying Client. This is to avoid Clients inheriting bad debt when they become a Paying Client. You will need to refund or credit any paid Invoices, or void any raised Invoices, in order to adjust the Paying Client.