CSS International Student's income

So I work as a tutor and earned around $500 last year. But in Vietnam we dont have tax or whatsoever related to this kind of work (I mean, I receive cash from clients.)
The money is small and I used it for my tuition expense in Vietnam so do I need to put it into student’s income on the CSS profile? I’m just afraid they will require I send some paper about tax to the IDOC.

Yes, you need to report it as income, because that’s exactly what it is. It doesn’t matter if it wasn’t taxed.