has anyone had any a request to change the subsidiary of an expense report? is it possible?

Normally, you can't change the subsidiary. Only case I know: If you change the associated employee in the Expense Report, for an employee profile in another subsidiary, the subsidiary changes to reflect the new employee selection.

makes sense. yea we have a strange request where an employee is issued a credit card from 1 subsidiary but they are located in a different one

Being there. In those cases I create a duplicate of the employee in the second subsidiary.