My college student worked a part time job last year. Where do I enter his income?

You do not report his/her income on your return. If it has to be reported, at all, it goes on his own return. If your dependent child is under age 19 (or under 24 if a full time student), he or she must file a tax return for 2021 if he had any of the following:

1.          Total income (wages, salaries, taxable scholarship etc.) of more than $12,550 (2021).
2.          Unearned income (interest, dividends, capital gains, unemployment, taxable portion of 529 distribution) of more than $1100.
3.          Unearned income over $350 and gross income of more than $1100
4.          Household employee income (e.g. baby sitting, lawn mowing) over $2300 ($12,550 if under age 18)
5.          Other self employment income over $432, including money on a form 1099-NEC

Even if he had less, he is allowed to file if he needs to get back income tax withholding. He cannot get back social security or Medicare tax withholding.

In TurboTax, he indicates that somebody else can claim him as a dependent, at the personal information section.

Thank you Hal_Al, your answer was so helpful and also answered some additional questions I did not even know I had! 😊 

State filing requirements may be lower.

Federal self-employment filing requirements are $400, not $432.

Self-Employed Individuals Tax Center | Internal Revenue Service (irs.gov)

@SweetieJean  Technically yes, but from a practical standpoint no.  Follow the calculations on Schedule SE. No tax is due unless your income was $433 or more.