When creating a new calculation no customer details are needed. You can just enter a name or identifier that makes sense - but before contract template can be exported we need more details. This requires that customer is onboarded on to KeyCore systems (an entirely internal KeyCore process). This ensures we have the correct address, corporate ID (CVR in DK) and so on.
Once Customer is onboarded you can select them from the dropdown and for customers with more than on billing entity select the correct one from the sub dropdown.