Residual reserves are what remain after the required reserves have been filled by a percentage of a bank's deposits are placed within the central bank. This excess reserve can eventually either be left at the central bank (at no interest rate) or used to create credit deposits to the general public. In this way, money as excess reserves will end up in another bank that also has to put the required reserves at the central bank. This process goes on until the ulitmate excess reserves add up to zero and the money creation process ends.