In the Czech Republic, it's pay slips/bank statements, or a work contract for mortgage (you cannot fire someone without a reason). There is a central government database of people who didn't pay a debt on time.

In Germany, also pay slips and work contracts. Additionally, there is a semi-private government-mandated company (I never understood why Germans don't complain about this) that maintains a database of existing debtors. You basically start with a perfect score and it decreases only when you don't repay on time.