Under what circumstances can an Aide for someone with Alzheimer's Dementia be taken as a deduction on the elder's taxes?

Or the caregiver as a medical expense for your sister?

Are you talking about taking sister as a dependent or her live in caregiver as a dependent?

Sorry I thought you mean you wanted to claim sister as a dependent. See your second question for the details.

You would have to provide MORE than half of their support. So if sis gets 800 a month in Social Security, you need to prove you spend MORE than 9600 a year supporting her. Now if you live with her, that is going to be hard to prove, since she is providing you with shelter.