To ensure money supply, some central banks require some or all of its foreign exchange receipts (generally from exports) be exchanged for the local currency. The rate that is used to purchase local currency may be market-based or arbitrarily fixed by the bank. This is generally applied in the countries where the currency is non-convertible or partially convertible.
The need for this tool is that the recipient of the foreign currency on conversion to local currency may easily dispose of these funds, may hold the funds with the central bank for some period or may be allowed to use these funds with certain restrictions. In simple words, the means to hold or use the foreign exchange may be otherwise limited.
Under this policy tool, money supply tends to increase when the central bank purchases the foreign currency by issuing/selling the local currency. This increase can be subsequently controlled through various issuances like selling bonds, foreign exchange interventions, etc.
Major Central Banks: Every country or a group of member states, for example European Union, shall have a central bank. Some of the major Central Banks are: