During the checkout process or earlier in the order process, the end users can select their country of origin. Example: https://shop.bls.ch/de/railway/abo/offer/?productId=1062
The list often does not contain all countries, because customers often only want to sell their products to people of certain countries. Customer then often request to add new countries to this list.
Method(s) of solution
New countries can be added in Peaksolution under System --> Config --> General --> General --> Country Options: