Can my 18 year old file with her son as a dependent if they both live with me?

[xmasbaby0 · Accepted solution]

A dependent cannot have a dependent.  If your 18 year old is your dependent, you should be able to claim her child as your dependent too, since you are supporting them.

[Hal_Al]

The money you hear about people getting for just filing a tax return claiming kids requires her to  have some earned income (wages or self employment). Without earned income, sh is not eligible for the "refundable" Earned Income Credit or Additional Child Tax Credit.
Even if she does have some earned income, it is usually best for the grandparent to claim both of them.

[bwa]

But if not your dependent, the answer is yes, she can (and you can't if she does.)