If you require medical treatment in the Netherlands, or you want to open a bank account or apply for welfare benefits, you have to be able to show proof of identity. You can do so by showing a passport or other identity document, such as an identity card.
Checking identity documents helps to fight fraud. On the street, the police may ask individuals to show proof of identity. If they see a cyclist riding through a red light, for instance. Anyone aged 14 or over must be able to identify themselves.