What term describes an instrument in writing that gives one person full power to act on behalf of another?

The term that describes an instrument in writing granting one person full power to act on behalf of another is a general power of attorney. This legal document provides the appointed individual, referred to as the agent or attorney-in-fact, with broad authority to manage the financial, legal, and business decisions of the person granting the power. This might include handling bank transactions, making investment decisions, managing real estate, and more. The scope of the powers granted in a general power of attorney is extensive, allowing the agent to perform nearly any action the principal could take in their personal capacity.

In contrast, a limited power of attorney would restrict the authority of the agent to specific tasks or periods, while a durable power of attorney is designed to remain in effect even if the principal becomes incapacitated but does not imply full authority unless specified. A special power of attorney is similar to a limited power of attorney, focused on singular or specific acts rather than broad powers. Therefore, the general power of attorney is the correct choice as it encapsulates the idea of full authority granted to an individual to act on behalf of another.