It takes two parties to create a valid power of attorney -- the principal and the agent. The principal is the person who delegates the authority to another to perform legal acts on his behalf, and the agent is the party who is authorized to perform these acts. The principal delegates authority to the agent by drafting and signing a power of attorney form. This form identifies the principal and specifies exactly which powers are delegated to the agent. Although not required in all states, it is a good idea to have your signature notarized in order to avoid challenges to the legitimacy of your grant of authority. Some states require you to use a government-drafted power of attorney form for certain purposes.
Regardless of whether your power of attorney is durable or non-durable, you normally have the right to revoke it at any time. One exception is that principals who are mentally incompetent or unable to communicate cannot revoke their power of attorney. But under the laws of many states, a power of attorney automatically expires if you become incompetent, unless either the power of attorney form specifically states otherwise or the circumstances indicate that you intended your power of attorney to endure even if you become incompetent.
Durable Power of Attorney
Because most power of attorneys are revocable, you cannot create even a durable power of attorney that cannot later be revoked. A durable power of attorney endures until the principal either dies or revokes the agent's authority -- but unlike non-durable powers of attorney, it does not automatically expire if the principal becomes incompetent. Although the form may or may not specifically state that the power of attorney is durable, it is easier to enforce if it specifically states that it will not expire even if the principal becomes incompetent. A durable power of attorney is commonly used by seriously ill patients to allow the agent to manage their affairs while they are unable to do so.
Non-Durable Power of Attorney
A non-durable power of attorney automatically expires under its own terms -- the principal doesn't have to die or revoke it in order for it to expire. Many types of non-durable powers of attorney exist. A power of attorney may, for example, authorize the agent to perform a specific act such as selling the principal's house while he is overseas; it will expire once the act is performed. Alternatively, it may expire on a particular date -- for example, a custodial power of attorney may empower an agent to perform legal acts on behalf of a minor child if his parents or guardians are incapacitated and expire on the child's 18th birthday.