@regordane Ahum. Let me introduce you to the general residence register (in Austria: Zentrales Melderegister or ZMR). So yes, in some countries the authorities absolutely do know where people live.
The UK has a very laxidazical approach to identity.
In many ways each govt department has their own approach to identity and often their own reference numbers.
The concept of a national id scheme was floated under Blair, but was very unpopular, for many reasons.
As such the election system effectively maintains it's own list of people, as does many other govt departments.