In Celoxis, clients can be arranged in an hierarchy. 
To define your Client hierarchy:
In the above example Express Pty Ltd is an Client with 3 client users (John, B Parry, Smith)
- First, create an client without login credentials for the client company (Express Pty Ltd).
- Now, create the client users (For e.g. John).
- For this login, under the Client Parent, select the client company name (Express Pty Ltd).
- Fill in the other details.
- Click Save.