Users can not be deleted in SOMAX but they can be inactivated.  Inactivating a user will remove the user from all Assignment Search and Lookup lists.  Additionally, if the user was a full user type then inactivating will "open" a full user license.

To Inactivate a User follow these steps:

Click| User Management

Click on the User Name you wish to Inactivate

Uncheck the for Is Active

Click Save