Classification tab in BP

Hi,

If I am using CRM standard role CRM000 to create a BP, I get the check box 'Customer' ticked by default in CRM 5.0v. But if I am creating a new 'Z" sold-to-party role and trying to create a business partner, the check box 'Customer' in classification tab is not selected -why is this so ? is it for the user to do or am I missing something in the config - appreciate your inputs

thanks

Kumar