My wife and I have done a good job teaching our daughter, now 15, that one does the right thing, simply because it's the right thing to do. This may not work for every child, but it did for us. Her motivation was never punishment, we explained that if she did the wrong thing, it's awful to have to live with that.
On one hand, THEAO's answer is correct, the stick the IRS wields is the audit and fines. I suppose from a legal standpoint, we comply with laws to avoid punishment. I find this to be unfortunate. To get back on topic -
- The extra regular income counts when applying for a mortgage, I recall you asking mortgage related questions, $10,000 in extra reported income will qualify you for over $45K in incremental mortgage borrowing.
- Depending how you file, the SE FICA contribution will add to your Social Security benefit, old Aerovistae will thank you for the extra income.
- Earned side income will let you open a Solo 401(k), again, that old Aero will be happier if you do that now.
I started with an answer more appropriate to Parenting because I have a very precocious child for whom I addressed this question a decade ago. The latter portion of my response helps to give tangible benefits which have value even if less than the tax you might be paying.