A power of attorney gives one or more persons the power to act on your behalf as your agent. The power may be limited to a particular activity, such as closing the sale of your home, or be general in its application. The power may give temporary or permanent authority to act on your behalf. The power may take effect immediately, or only upon the occurrence of a future event, usually a determination that you are unable to act for yourself due to mental or physical disability. The latter is called a “springing” power of attorney. A power of attorney may be revoked, but most states require written notice of revocation to the person named to act for you.