A Power of Attorney is a written document that allows an appointed agent (formally called the attorney-in-fact) to act on behalf of the person who gave the power (formally called the principal). The scope of the Power of Attorney is generally quite broad to allow the attorney-in-fact to make all the financial decisions and execute the related transactions that the principal would have the power to do with his or her own property. However, it is possible to limit a Power of Attorney to very specific duties, such as to pay bills for day to day living expenses or to sell a certain parcel of real estate.

A durable Power of Attorney continues in effect once a person becomes disabled or incapacitated. Generally, a person executes a Power of Attorney while in good health, anticipating that someday their health will fail or they may have an accident and will have the need for someone else to manage their business affairs. Oftentimes, the Power of Attorney does not become effective until the principal's physician certifies that he or she is disabled. By doing this, the attorney-in-fact has no power until the certification from the physician is issued.

If a person becomes disabled or incapacitated without a Power of Attorney in effect, the spouse or family has little choice but to open a court supervised conservatorship and/or guardianship. This can be a very expensive process to accomplish the same goals that a Power of Attorney would have accomplished. See question explaining Conservatorships and Guardianships. A Power of Attorney becomes ineffective at the death of the principal and the probate procedure takes effect.