Dear Liz: My husband has Parkinson’s disease and is showing early signs of dementia. I’ve been advised to get a financial power of attorney. If all of our accounts are joint, is this necessary? What will that do for me?

Answer: A power of attorney gives you the authority to make decisions on your husband’s behalf. You wouldn’t need one to pay the bills from your joint accounts, but this document could be invaluable if you wanted to take action on jointly held property, such as selling a car or house or refinancing a mortgage. Otherwise, you might have to go to court to get a guardianship, which can be expensive.

Please don’t wait. For the document to be valid, your husband needs to be able to understand what a power of attorney is and what it does. You’ll also need a power of attorney for healthcare, which is sometimes called a healthcare proxy or advanced directive, to make decisions regarding his medical care.

There are do-it-yourself options, but given your husband’s condition you may want to hire an experienced estate planning attorney who can offer personal guidance and help make sure the documents won’t be challenged.