A replacement banknote, commonly referred to as a star note, is a banknote that is printed to replace a faulty one and is used as a control mechanism for governments or monetary authorities to know the exact number of banknotes being printed. Also, since no two serial numbers can be the same, the bill is simply reprinted with a symbol in the serial number, identifying it as a replacement for an error note. Replacement bills have different symbols to mark the error around the world, although the most popular examples are "star notes".