You are correct; if his total eared income is less than $15,750, he does not even need to file a federal return.
Someone who can be claimed as a dependent must file a tax return for 2025 if he had any of the following:
- Total income (wages, salaries, taxable scholarship etc.) of more than 15,750 (2025).
- Unearned income (interest, dividends, capital gains, unemployment, taxable portion of 529 distribution) of more than $1350.
- Unearned income over $450 and gross income of more than $1350.
- Household employee income (e.g. baby sitting, lawn mowing) over $2600 ($17,750 if under age 18)
- Other self employment income over $432, including money on a form 1099-NEC
