A dependent cannot claim a dependent. If your daughter was 18 at the end of 2019 then she can be claimed as your dependent, which means she cannot claim a child as her dependent. YOU can claim the grandchild on your own return. If your daughter can be claimed as a dependent (and she can be) the rule is she must say on her own return that she can be claimed as someone else's dependent.
There is no such thing as a "full" dependent or a "partial" dependent. She is either a dependent or she is not. And she is. She is 18 and she lives under your roof. If you receive child-related credits for claiming your grandchild and choose to share those with your daughter, you may do so.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
