The 1993 SNA recommends that the services of central banks be measured on the basis of receipts from fees, commissions, and financial intermediation services indirectly measured (FISIM). This method sometimes results in unusually large positive or negative estimates of output. In 1995, the ISWGNA therefore decided to allow countries to measure the output of central banks, as a second best, at cost. However, the ISWGNA did not provide further guidance on the implications of this method. The review seeks to clarify the impact of the different roles that central banks perform on the nature of their output and the appropriate valuation and allocation to associate with the output of central banks.