Identity Card (also called a piece of identification or ID, or colloquially as one's 'papers') is any document which may be used to verify aspects of a person's personal identity. If issued in the form of a small, mostly standard-sized card, it is usually called an identity card (IC). In some countries the possession of a government-produced identity card is compulsory while in others it may be voluntary. In countries which do not have formal identity documents, informal ones may in some circumstances be required.