If a kid is old enough to work, a kid is old enough to file a required tax return. Babies even file tax returns. There is no lower age limit.
Every year on this website at least once, some kid mentions how she wrote a college application essay about her self-employment job (tutoring, piano lessons, apartment cleaning, golf caddying, summer nanny)- - how it taught her values, and organizational skills, etc, etc,; but then turns around and lets slip that the money earned from this job was not reported on her tax return. Apparently the job did not teach her to avoid failure to file penalties. I think it’s a red flag especially for need-based scholarships where clearly the applicant has a job, yet no tax return was filed.
Last cycle there was a mom whose son was applying for the Evans Scholars program (golf caddy) which is need based. Both she and her son needed to complete financial/tax information for the application, including CSS profile. On CC, she learned (since it apparently wasn’t obvious) that because of the few thousand he earned in summer caddying, including tips, he needed to file a tax return, including Schedule C, so she and her son quickly took care of his tax return filing. Later she reported back that he was fortunate to be named an Evans Scholars at his school of choice. I believe that the scholarship selection committee would find it quite odd that a kid applying for this scholarship did not file a tax return. It says something about character. In fact for this scholarship, one of the requirements is that the applicant demonstrate outstanding character and integrity.
If this Questbridge applicant earned more than $400 cleaning apartments in 2015, she is required to file a tax return to report her self-employment income. Whether her parents get EIC has no effect on the amount of self-employment tax she owes on her own cleaning income.