You cannot amend for a better refund for more than three years back. As for whether you can claim your grandma as a dependent-----that will be based on how much income she was receiving and whether you paid for over half her support. Being her "primary caretaker" may not necessarily mean you can claim her as a dependent.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
Provide us with some details about how much income Grandma had---not including any Social Security. And...whose home did she live in---her own--or yours?
**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.**
