In Koha-Suomi libraries we use cardnumbers as userids. This is done with a database trigger which sets cardnumber as userid when user is saved to database. Mostly this works well, but occasionally we have faced problems with patrons seemingly having no subpermissions. Patrons subpermissions are fetched from database with method get_user_subpermissions based on their userid. So even if they are saved in database they are not displayed in Koha's UI if userid is missing. While this isn't a major problem it can be confusing for staff members if they have accidentally created a patron without cardnumber/userid and then try to save permissions for them which seemingly are not saved. Also full permissions for patrons are still displayed normally so for consistency it would be logical to use borrowernumber to fetch subpermissions instead of userid. Method get_user_subpermissions is used in two places, member-flags.pl to fetch subpermissions and about.pl to check that SCO patron doesn't have extra permissions. As far as I can see changing it to use patrons borrowernumber shouldn't have any dramatic side effects.