If either child made $400 or more in self-employment income, they must file a return of their own.
Dependent filing requirements
When other taxpayers, such as your parents, are eligible to claim you as a dependent on their own tax return, you still may need to file your own return — but you can't claim a personal exemption. You will need to file a return if your earned income is greater than the standard deduction amount for the single filing status.
However, if the total of your unearned income is more than $1,000, you need to file a return even if it is not required by your earned income. Unearned income covers all other earnings, such as taxable interest, dividends, and capital gains that aren't the result of performing services.
Special filing situations
Regardless of special circumstances, you are expected to file a tax return if you owe taxes other than income tax. These taxes include Social Security taxes, alternative minimum taxes, or household employment taxes. Other situations where you will also have to file are if you're self-employed and earned at least $400 during the year, or if you received distributions from a health savings account.
