What is reserve requirement?
Reserve requirements are central bank regulations that set the minimum amount that a commercial bank must hold in liquid assets. This minimum amount, commonly referred to as the commercial bank's reserve, is generally determined by the central bank on the basis of a specified proportion of deposit liabilities of the bank. This rate is commonly referred to as the reserve ratio. Though the definitions vary, the commercial bank's reserves normally consist of cash held by the bank and stored physically in the bank vault (vault cash), plus the amount of the bank's balance in that bank's account with the central bank. A bank is at liberty to hold in reserve sums above this minimum requirement, commonly referred to as excess reserves.

The reserve ratio is sometimes used by a country’s monetary authority as a tool in monetary policy, to influence the country's money supply by limiting or expanding the amount of lending by the banks. Monetary authorities increase the reserve requirement only after careful consideration because an abrupt change may cause liquidity problems for banks with low excess reserves; they generally prefer to use open market operations (buying and selling government-issued bonds) to implement their monetary policy. In the United States and many other countries (except Brazil, China, India, Russia), reserve requirements are generally not altered frequently in implementing a country's monetary policy because of the short-term disruptive effect on financial markets.
O que é o requisito de reserva?
Os requisitos de reserva são regulamentos do banco central que estabelecem o montante mínimo que um banco comercial deve manter em ativos líquidos. Este montante mínimo, comumente referido como reserva do banco comercial, é geralmente determinado pelo banco central com base em uma proporção específica de passivos de depósito do banco. Esta taxa é comumente referida como a taxa de reserva. Embora as definições variem, as reservas do banco comercial normalmente consistem em dinheiro detido pelo banco e armazenado fisicamente no cofre do banco (caixe de cofre), mais o valor do saldo do banco na conta do banco com o banco central. Um banco está livre para manter em reservas acima desse requisito mínimo, comumente referido como reservas excessivas. A taxa de reserva é às vezes usada pela autoridade monetária de um país como uma ferramenta na política monetária, para influenciar a oferta de dinheiro do país, limitando o montante da reserva monetária.