This is directly from Publication 559 from the IRS

"All personal representatives must include fees paid to them from an estate in their gross income. If you aren't in the trade or business of being an executor (for instance, you are the executor of a friend's or relative's estate), report these fees on your Form 1040, line 21. If you are in the trade or business of being an executor, report fees received from the estate as self-employment income on Schedule C, Profit or Loss From Business; or Schedule C-EZ, Net Profit From Business, of your Form 1040."