Yes, you can select the appropriate home nation for residence when you first set up a client.
Alternatively, it can be input in the 'Taxes' screen. Select the appropriate person in the 'People' box then expand the 'Residence' menu. Select 'Scotland' from the menu, then click 'Add'.
Note that if there is already a 'Taxes' item in the Ledger for that person, you will need to select that first and edit that entry rather than create a new one.