Huizi 會子 was a type of paper money circulating in the region of Liang-Zhe 兩浙 (today's Zhejiang and at that time the surroundings of the capital Lin'an 臨安, i.e. Hangzhou), and from 1160 on issued by the Ministry of Revenue (hubu 戶部) and controlled by the Paper Notes Office (huiziwu 會子務). The first evidence of huizi notes dates from 1075, as a common means of payment on the markets in Shaanxi. "Comfortable money" (bianqian huizi 便錢會子) was widespread in Hangzhou and the surroundings in the early decades of the Southern Song period 南宋 (1127-1279). The use of huizi spread to the north and west, and it was both welcome for market transactions as well as for tax payment, and became the most important kind of paper money in the Southern Song empire, besides the jiaozi 交子, qianyin 錢引 and guanzi 關子. Between 1161 and 1166 the office printed paper notes with a total value of 28 million dao 道 (guan 貫, i.e. 1,000 copper cash).
During the reign of Emperor Xiaozong 宋孝宗 (r. 1162-1189) a discussion about the use of huizi ended with the diagnosis that paper notes were direly needed by the local markets to supply the amount of copper cash, which seems not to have sufficed to satisfy the booming economy. At that time, paper notes with a value of 4.9 million guan were circulating on the markets and used for everday payment. The emperor therefore decided to supply the market regularly with new paper notes, and to replace them in regular intervals by fresh ones. The worn-out ones were not in all cases destroyed, but continued to circulate at a discounted rate. The amount of paper notes in use thus constantly rose.
The first note was denominated in one guan, but in 1163 smaller denominations were introduced, in 200, 300 and 500 wen 文 (copper cash). The lifecycle was restricted to three years, a period after which the Ministry issued an amount of 10 million guan of fresh huizi notes. Huizi were convertible into copper coins. Yet in practice, fresh notes were produced only in a nine-years turn, but issued in double amounts. In 1176 and 1190 twenty million guan of paper notes were thrown into the market, and in 1195 the volume of money produced per period was raised 30 million. As might be expected, the number of circulating notes was quite high. In the very early 13th century, no less than 41 million min 緡/guan of paper money were circulating, in 1209 as much as 115.6 million, and in 1231 even 329 million. This of course caused a depreciation of the paper money, aggravated by the easy mode in which the three-coloured notes could be forged. As word was going, a 200-wen note was worth less than a straw sandal in the late Southern Song period. In fact, one guan was just appreciated at 3-400 wen. People therefore began to hoard copper coins, and quite an amount of copper cash left the Song empire and flew to the northern markets of the Jin empire 金 (1115-1234). In order to finance their war against the ever more aggressive Mongol armies, the Song government threw ever more paper bills on the market.
In some regions the huizi note differed from the standard one, like the Hubei huizi 湖北會子 (with just two denominations, 1,000 and 500, and a volume of 7 million min), Hu-Guang huizi 湖廣會子, Zhibian huizi 直便會子, or the iron-cash huizi 鐵錢會子 (with just three denominations, 300, 200 and 100) circulating in Jinyang 金洋, close to Xingyuan prefecture 興元府. From 1137 on a silver note (yin huizi 銀會子) was circulating in Sichuan and Shaanxi. It was denominated in weight (of silver), with the types 1 qian 錢 and 1.5 qian (see weights and measures). They were replaced annually. The Jin dynasty in the north also produced huizi paper notes.