I had my taxes filed by an individual company..... durring the conversation she was telling me that she could get me more money by listing my 16 year old sister on the return as a dependant.... so I gave her thessn so she could show me the difference and I told her I didn't want to do them that way.... long story short I signed them and got my return and paid bills and then got to thinking about it and when I looked over my return my sister was listed on there I would like my mom to still be able to use her as a dependant and I don't want to get in any trouble I could pay the money back in payments what should I do

You should amend your tax return by filing Form 1040X and removing your sister. You will owe more tax and should pay the tax with the filing of the amended tax return. Your mother may have difficulty filing electronically and claiming your sister as a dependent because you have already claimed her. Your mother may need to file by paper.

Get you 1040X in before April 15 (with any additional payment that may be due) and there should be no problem.

But first, please answer this - who is legally entitled to claim your sister as a dependent? Do you provide more than 50% of your sister's support? Or does your mother? Do you all live in the same house? Who pays for the house upkeep?