Google:

Dependent tax filings

All taxpayers who are claimed as a dependent on someone's tax return are subject to different IRS filing requirements, regardless of whether they are children or adults. A tax return is necessary when their earned income is more than their standard deduction. However, the threshold decreases to income greater of $1,050 or the sum of $350 and the person's earned income. A dependent's income is unearned, when it comes form sources such as dividends and interest.