A power of attorney (POA) or letter of attorney is a written authorization to represent or act on another’s behalf in private affairs, business, or some other legal matter. The person authorizing the other to act is the principal, grantor, or donor (of the power). The one authorized to act is the agent or, in some common law jurisdictions, the attorney-in-fact. Both the principal and agent act according to the written terms and conditions in the letter.
Depending on the jurisdiction, a power of attorney may be oral and in writing and, whether witnessed, will hold up in court. The Uniform Power of Attorney Act employs the term agent. As an agent, an attorney-in-fact is a fiduciary for the principal, so the law requires an attorney-in-fact to be completely honest with and loyal to the principal in their dealings with each other.
In order for a power of attorney to become a legally enforceable document, at a minimum it must be signed and dated by the principal. Some jurisdictions also require that a power of attorney be witnesses, notarized, or both. Even when not required, having the document reviewed and signed (and often stamped) by a notary public may increase the likelihood of withstanding a legal challenge.
If the attorney-in-fact is being paid to act on behalf of the principal, a contract for payment may be separate from the document granting power of attorney.