Another was to use foreign currency: the bank could lend, or accept a bill of exchange, in one currency and collect its debt in another, building a hidden rate of interest into the exchange rate.

For example, if a company knows that will need a particular foreign currency to pay a bill in a month's time, a forward deal enables it to protect itself.

Because of RMB's excess issue through "foreign currency assets - RMB" model in China, Central Bank Bill as a debt tool has been replacing the excess currency.