Should I use my mother's turbo tax account if my mother passed away, father (mentally impaired) is still alive and I am their representative

Yes, that would give you the advantage of seeing what had gone on in the past and give you some idea of the information to look for.  It may be to your advantage to review some of these articles.

If you think your parent may need someone trustworthy to act on his or her behalf, this is the article you should read. Here are 12 essential steps for getting the authority to handle your parent's financial and/or healthcare affairs:

• Understand what the law allows (and doesn't allow)
• Learn about "capacity" and evaluate your parent's condition
• Familiarize yourself with the various types of power of attorney
• Discuss the issue with your parent (and possibly with other family members)
• Consult with your parent's financial institutions and/or healthcare providers
• Hire an estate or elder law attorney (optional but recommended)
• Help your parent choose the best course of action
• Mind all the details when drafting the paperwork
• Get the final document notarized (or signed in the presence of witnesses)
• Make multiple copies of all necessary documents and keep them safe
• Present yourself correctly when using your power of attorney
• Consider pursuing adult guardianship if your parent already lacks decision-making capacity

Nothing here constitutes legal advice. Please consult a lawyer who specializes in estate or elder law for up-to-date information and advice about your particular situation.

How to Get Power of Attorney for a Parent (Without Overstepping)

If this does not completely answer your question, please contact us again and provide some additional details.