Jiaozi was a form of promissory note which appeared around the 11th century in the Sichuan capital of Chengdu, China. Numismatists regard it as the first paper money in history, a development of the Chinese Song Dynasty. Early Jiaozi notes did not have standard denominations but were denominated according to the needs of the purchaser and ranged from 500 wén to 5 guàn. The government office that issued these notes or the Jiaozi wu (交子務) demanded a payment or exchange fee (紙墨費) of 30 wén per guàn exchanged from coins to banknote. The Jiaozi were usually issued biannually.