Financial and Legal

Asking a question on behalf of a caregiver without internet or email access. Her friend / neighbor has been diagnosed with dementia. Based on the description it sounds like early stage and may still have capacity to make decisions. The care recipient originally, signed a POA that gave control of her finances to her sister. Based on the description of the friend, the sister has not done a good job providing support and access to funds. The client is interested in making a change to her POA. What is the process and requirements to make a change to a POA?

Thanks!