The use of paper currency was initiated by merchants. To avoid having to carry thousands of strings of coins long distances, merchants in late Tang times (c. 900 CE) started trading receipts from
deposit shops where they had left money or goods. The early Song authorities awarded a small set of shops a monopoly on the issuing of these certificates of deposit, and in the 1120s the government
took over the system, producing the world’s first government-issued paper money