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?
