A letter of attorney is a legal document that gives one person the authority to act on behalf of another individual. There are many synonyms for the term letter of attorney, including power of attorney, letter of authorization, authority letter, legal mandate, and letter of representation. A power of attorney is a written authorization giving someone the ability to act on behalf of another person in legal or financial matters. An authority letter is a document that confers authority to a person to act on behalf of another person. A legal mandate is a written order for an individual to carry out specific actions on behalf of another person. A letter of representation is a document that gives a person the power to represent another individual in legal matters.