You do need an attorney, though not necessarily a tax attorney. Tax attorneys are generally used to represent someone in Tax Court after an audit. You do need to get her back taxes filed, and if there are a lot of medical expenses, that may reduce her tax bill considerably. I'm assuming that your brother had a POA to handle her affairs. If he did siphon off money for his own benefit, that is a misuse of the POA and can be prosecuted through the courts. There's also something called "fiduciary responsibility" that goes along with that which requires that all matters, financial and otherwise, are handled in a prudent manner including filing her taxes, paying bills appropriately and on time, providing adequate medical care, safeguarding her assets, etc.