Article 38 of the "General Principles of Civil Law" stipulates: In accordance with the law or the articles of association of a legal person, the person in charge who exercises functions and powers on behalf of the legal person is the legal representative of the legal person. Article 50 of the Contract Law stipulates: If a contract is entered into by a legal representative or responsible person of a legal person or other organization who exceeds his or her authority, the representative act shall be valid unless the counterparty knows or should know that he or she has exceeded his or her authority. According to the above provisions, a contract with only the signature of the legal representative and no official seal of the unit is also valid. However, if the legal representative or person in charge of a legal person or other organization enters a contract beyond his authority, and if the counterparty knows or should know that he has exceeded his authority, the representative act shall be invalid. .