Negative Interest Rates

They exist:

Bills of 1, 2, 5, 10, 20, and 50 Chiemgauer were issued. Each one is equivalent to respectively to 1, 2, 5, 10, 20, and 50 euro. To maintain them in circulation, every three months, you have to put on the banknotes a "scrip", corresponding to the 2% of the banknote value. This system, called demurrage, is a sort of currency circulation tax.