Do I have to carry an ID?

In Poland, there is no legal obligation to carry an identity card. However, it is recommended, as various organs are entitled to check it in order to determine a person's identity. Documents are necessary for any bank operations, collecting packages at the post office, or signing a rental contract for a flat. They are also frequently checked in clubs or shops  when buying alcohol or cigarettes. 

When crossing a state border, a person is obliged to present their documents:  a passport, an ID card and a visa, if required.