Assuming this is for a Residual commission and your 1099-Misc has the amount in box 7, instead of box 3; The income is taxable (you cannot write it off) but may not be subject to self employment tax. You may have to use a work around in TurboTax (TT).
Do not enter on Schedule C. Do not enter it as a 1099-MISC, even though you received a 1099-MISC. Here's how to enter a residual commission in TurboTax. This will work in both TurboTax Online and the CD/download version. No override is necessary.
Click the Federal Taxes tab.
Click Wages & Income.
Click I'll choose what I work on
On the screen "Your 2018 Income Summary," scroll all the way down to the last section, "Less Common Income."
Click the Start or Update button for the last topic, "Miscellaneous Income, 1099-A, 1099-C." (I know you have a 1099-MISC, but this is the topic you want.)
The next screen says "Let's Work on Any Miscellaneous Income." Scroll all the way down to the bottom and click the Start or Update button for the last topic, "Other reportable income."
The next screen asks "Did you receive any other taxable income?" Click Yes.
On the next screen, "Other Taxable Income," it says "Do not enter income reported on Form 1099-MISC." Ignore that. For the description enter "1099-Misc residual commission" and enter the amount. Click Continue.
On the next screen click Done.
On the next screen click Continue.
The income will be reported on Form 1040 line 21 (schedule 1) with the description that you entered. By identifying it as a residual commission, you will hopefully avoid any inquiries from the IRS.
The alternative is to attach a statement explaining the circumstances.
An even better alternative is to get a corrected 1099-Misc, with the amount in box 3.
