Notgeld (German for "emergency money" or "necessity money") refers to money issued by an institution in a time of economic or political crisis. The issuing institution is usually one without official sanction from the central government. This occurs usually when sufficient state-produced money is not available from the central bank. Most notably, notgeld generally refers to money produced in Germany and Austria during World War I and the Interbellum. Issuing institutions could be a town's savings banks, municipality and private or state-owned firms.
Notgeld was mainly issued in the form of (paper) banknotes. Sometimes other forms were used, as well: coins, leather, silk, linen, postage stamps, aluminium foil, coal, and porcelain; there are also reports of elemental sulfur being used, as well as all sorts of re-used paper and carton material (e.g. playing cards). These pieces made from playing cards are extremely rare and are known as Spielkarten, the German word for "playing card".
Notgeld was a mutually-accepted means of payment in a particular region or locality, but notes could travel widely. Notgeld is different from occupation money that is issued by an occupying army during a war.