https://www.blakelywalters.com/resource-center/tax/does-your-child-need-to-file-a-tax-return
Here's an example. Kyle is a 20-year-old college student who's claimed as a dependent by his parents. He received $400 in unearned income and $5,500 for a part-time job on campus. He does not have to file a tax return because both his unearned and earned income fall below the thresholds. Kyle's total income of $5,900 is less than his total earned income plus $400.