Can I claim my sister as my dependent even though my dad did not?

[Alphmega-K]

Sorry, forgot to add details.

So, my sister lives with me full time and I pay for her food and school.  My dad, a widow, gets my sister's social security, and previously has claimed my sister as his dependent.  Last year he married and while they lived with me for half the year and he pays my mother's social security to house bills (from our mother, who passed away when my sister was 8), this year he retired and is on disability due to work injuries and will probably not go back to work, as he is three years away from social security and has other health issues (He is 62 now).  Several family members have suggested that I should claim her this year.

He is still legally her father but she is living with me so she doesn't go out of school district.  While he never gave me custody or anything, I also take her to all her doctor appoints and has made contacts with the school and insurances to list me as someone aloud to contact as, again, he is disabled and it's hard for him to take her to these things.  And while he hasn't given me any form of written permission to claim her as a dependent, he already filed his taxes and did not claim her and wouldn't have a problem if I did.  

Do I need to get written permission first or should I just claim her and if the government audit?

[KittyM · Accepted solution]

It depends.  You may be able to claim your sister as a "Qualifying Relative."  The requirements for a Qualifying Relative are below:

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,050 in 2017.
• You provided more than half of their financial support. More info

When you add someone as a dependent, TurboTax will ask a series of questions to make sure you can claim them.  This is the easiest way to determine if someone is your dependent. 

[Alphmega-K]

Posted some detail.  Do I still qualify?

[macuser_22]

If she is under age 19 (or under 24 and a full time student) and did not support herself then you probably can claim her as a "Qualifying Child" if she lived with you more than half the year.