Shareholders, debt holders and regulators need to be able to size up the amount of capital the bank is targeting, how this compares to the minimum and how much capital is currently available on the balance sheet.

FORBES: The Future Of Banks Hangs In Their Balance Sheets

Banks must maintain a minimum amount of capital (equity, mainly) in relation to their loans: the riskier the loans, the more capital they must have.

ECONOMIST: Economics focus

Regulators say holding back a small amount of customer cash would decrease the amount of capital that firms would have to hold in reserve and compare the idea to a minimum account balance required by banks.

WSJ: U.S. Sets Money-Market Plan

On the basis of a pact between central bank governors and senior regulators, every important developed and developing country has agreed to enact laws to raise the amount of capital that banks have to hold as protection against future losses to more than treble the current minimum.

BBC: Why have we left bank reform to technocrats?