dependents

Can my girlfriend who is claimed by me on my return, also file a separate tax return so she can get Child Credit for her child? She qualifies as a dependent on my return, so does her child. But since her child is not related to me, I am only entitled to $500 dependent credit on my return. But she could get up to $2000 in child credit if she is able to also file a separate tax return while being claimed on my return.