Can I file head of household if my granddaughter lived with me rent free while attending college?

[DanielV01]

Probably not.  Even though your granddaughter stayed with you, she is still considered to live with her parents because she is in school, which is a temporary absence.  They are still allowed to claim her as their dependent, and if they do, you cannot claim Head of Household.

Even if they do not claim her, you can't claim her as your dependent unless you make more money than their average.  For instance, if the husband makes 40,000, and the wife 20,000, you have to make more than 30,000 to claim her.  If those conditions do exist, then you may be able to claim her as your qualifying child and head of household.