As an off-setting asset it holds the note of its customer receivable at some future time.
Sec.7.

#Nature of banking reserves#.

Banks would have nothing to gain by receiving deposits or by issuing notes if they were obliged to keep in the vaults actual money to the amount of their deposits and outstanding notes (unless they were paid by depositors for taking care of deposits).

Banks have found it necessary in practice to keep on hand money amounting to only a fraction of all their outstanding obligations in order to be able to pay promptly all due demands, excepting in periods of general financial distress.

The sum thus kept on hand is called the _reserve_ or the _reserves_ of the bank, and this is frequently expressed as a percentage of reserves against deposits or against note issues, respectively.