Nonemployee compensation on a 1099-MISC is self-employment income and needs to usually be reported on Schedule C (or Schedule F if it is farm income) even if you are just doing a little bit of work on the side and do not have an official business. The IRS considers any income reported in Box 7 of the 1099-MISC as self-employment income and looks for it to be reported on either Schedule C or F.
If you received a Form 1099-MISC with nonemployee compensation but you should've received the income on a W-2, you don't need a Schedule C for your 1099-MISC. We'll ask you questions to determine the amount of the Medicare and Social Security taxes that should've been collected as an employee. Form 8919 Uncollected Social Security and Medicare Tax on Wages