The percentage of the assets that were spent to run a mutual fund (as of the last annual statement). This includes expenses such as management and advisory fees, overhead costs and 12b-1 (distribution and advertising ) fees. The expense ratio does not include brokerage costs for trading the portfolio, although these are reported as a percentage of assets to the SEC by the funds in a Statement of Additional Information (SAI). the SAI is available to shareholders on request. Neither the expense ratio or the SAI includes the transaction costs of spreads, normally incurred in unlisted securities and foreign stocks. These two costs can add significantly to the reported expenses of a fund. The expense ratio is often termed an Operating Expense Ratio (OER).