No, as it's already deducted from your mutual fund taxable gain. It may seem like mutual fund expense ratios all into the investment expense category, but there is a catch. Miscellaneous expenses are only deductible if they produce or collect taxable income that can be included in your AGI. Specifically, page 10 of Publication 529 states, "You can deduct investment fees, custodial fees, trust administration fees, and other expenses you paid for managing your investments that produce taxable income."

BUT, in the case of mutual fund expense ratios, IRS rules indicate the fees paid to investment managers reduce a person's AGI and are therefore not deductible. For example, a stock fund that returned 10% and had an expense ratio of 1% results in a taxable gain of 9%. Investment fees are already being taken out of the AGI equation so deducting them on your tax return is double-dipping.

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