@macuser_22 Thank you very much for the reply and the explanation about the dating on the original question. I read p. 200 of publication 17 (for 2018), which, as you point out, is irrelevant given that a child who previously (that is, before TCJA) would have paid the relevant parent's rate on her (I'm assuming the child is female) unearned income now pays the trust rate. But my question really is about whether a 19-year old student who is completely self-supporting (and indeed who may support her only living parent) but whose EARNED income provides only a small portion of her support must file form 8615. And if she does have to file that form, is she simply supposed to leave lines A and B empty? It doesn't seem right (and I don't mean by that that it doesn't seem fair, although that's true too, but that it seems like I must be getting something wrong) that such a person has to pay trust rates on unearned income while a similarly situated 25-year old does not. But, that does seem to be what the instructions for 8615 say. Of course, if the word "child" in 8615 means *qualifying child*, then the 19-year old that I am thinking of would pay regular single-filer rates and not have to fill out 8615, since she would be no one's qualifying child. (Maybe one way to make my question clear is this: Suppose a person who was abandoned by her father on the day she was born inherits money from her mother, who dies very young, but after the child turns 18. Does this person really have to pay trust rates rather than single-filer rates on unearned income due to the fact that her father is alive?)
