By definition, it's NEC. But the operation tells you if that is a business type of operation or not; the Form doesn't define this. Facts and Circumstances define that for your taxpayer. SE tax isn't the issue. You might have only $400 in reportable Gross. It's the function or operation that matters. What did they get paid for doing? Sched C is where you enter the income and related expenses when it relates to a business activity. Does that describe this for that taxpayer?