In brief
A will deals with your wishes after death. An LPA appoints someone to make specified decisions during your lifetime. They serve different purposes, so having one does not replace consideration of the other. LPA rules described here apply to England and Wales.
Two documents, two different moments
A will records how you want your estate to be distributed after death and names executors. A lasting power of attorney (LPA) is an arrangement for decisions during your lifetime if you ever lose the mental capacity to manage your affairs. Making one does not replace the need to consider the other.
Who can make decisions for you?
In England and Wales, separate LPAs cover Property & Financial Affairs, and Health & Welfare. They must be made while you have full mental capacity and registered with the Office of the Public Guardian before use. Without an LPA, your loved ones face expensive and lengthy Court of Protection proceedings.
A practical starting point
Think about the people you trust, the responsibilities involved and any existing documents. Marriage, welcoming children, moving home or a change in family dynamics are all key moments to review your arrangements.
Source: GOV.UK: Lasting powers of attorney