Enter 1099-K info for a child?

Q. Do I need to claim this?

A.  No, neither on his return or yours. The reason is: because the amount is under $1300. 

That's the simple answer.  The real answer is more complicated. For background, see the standard dependent income answer below the line.

Whether he has to file or not hinges on the question: Is this self employment income (item #4 below).  It sounds like work, and work not reported on a W-2 is usually self employment.  But, based on the circumstances and the fact that the organization issued a 1099-K, instead of a 1099-NEC, you are safe in calling it "other income"  and that limit is $1300.

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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 2024 if he had any of the following:

1. 1.  Total income (wages, salaries, taxable scholarship etc.) of more than $14,600 ($13,850 for2023).
2.  Unearned income (interest, dividends, capital gains, unemployment, taxable portion of 529 distribution) of more than $1300 ($1250 for 2023). 
3. Unearned income over $450 and gross income of more than $1300.
4.  Household employee income (e.g. baby sitting, lawn mowing) over $2600 ($14,600 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..

If his only income is from interest and dividends, Alaska PFD or capital gains distributions shown on a 1099-DIV, there is a provision for entering it on your return, using form 8814. Enter at Less common income / Child's income.