My 20 year old daughter and her 5 month old daughter live with me full time and I provide all their support. Can I claim them as dependents for tax purposes?

You can claim both provided your daughter earned less than $2,400 for the entire year and they are both US citizens.

Am I correct in understanding that because she is over 19 and not a student, I can't claim her even if she earned less than $2,400?

You CAN claim her as a dependent regardless of her age provided she did not make more than $2,400. You can claim both of them.

Your child can be any age to claim them as a dependent provided they lived with you in your home and you provided food and housing for them for a certain amount of time during the year.

If YOU make less than a certain amount you could possibly be eligible for an earned income credit for both of them. Check it out and see if you qualify for this. You don't have to be married to get this earned income credit. You just have to make less than a certain maximum to qualify for this. Who knows, you may just be getting back more money this time around.

A dependent can be your qualifying child or qualifying relative. A Qualifying Child must be under 19 or 24 if full time student. There is no age limit for a qualifying relative, and it is not required that the dependent (who is related to you) lives with you. You must provide more than half of the support and the person did not earn more than $3650 in 2009. Your U.S. Tax Return: Requirements for claiming a dependent

The child is your qualifying child and you Ill get EIC and child tax credit.