When a child who dependent on their return and under age 19 or under age 24 and a full-time student , must file their own taxes, if the child satisfying following conditions:
• Totally self- employment earnings are more than $400.
• Gross income is above $950 or earned income (up to $5,800) plus $300.
• Earned income above $5,800.
• Unearned income above $950.
If a child is a full time student then at the age of 24, he has to start paying the taxes else the age is 19 years and it also depends on the income of the child if he is above 24 and his salary is above $400, then he has to the taxes separately from his parents.