Article 32 of my country's "Contract Law" stipulates: "Where the parties conclude a contract in the form of a contract, the contract is established when both parties sign or seal it." As far as the parties are concerned, they are nothing more than natural persons, legal persons and Other organizations. When a natural person concludes a contract, the natural person who concludes the contract generally signs or stamps his or her name. When a legal person or other organization concludes a contract, the legal representative or the person in charge of another organization generally signs or stamps the contract with the official seal of the unit. Therefore, theoretically speaking, whether it is a natural person or a legal person, as long as it is signed or stamped, it is enough to choose one of the two.

However, according to general practice and trading habits, as a legal person, it is generally required not only to have the seal of the unit, but also to add the signature of the legal representative. Because only two things will ensure the reliability of the contract signing. We can speculate based on common sense, how could a single seal be obtained? It may be that the company's official seal was not properly managed and was stolen by others, so there will be no signature of the legal representative. And what can a single signature mean? It is likely that someone else is pretending to be the signature of the legal representative of the unit. Therefore, there is often only a single signature or seal, which is less convincing. The other party will think that there may be suspicion of fraud. Of course, both of them may also be suspected of fraud, but this probability is still relatively small. We would rather believe in the authenticity of signatures and seals.

Theory is theory. In practice, people ask you to have both. What can you do? And in practice, many places require signatures and seals at the same time. The key is to look at what the other person wants.

As for the power of attorney you mentioned, with the power of attorney, the other party has absolute reason to believe that the agent has the right to represent the company and exercise corresponding business rights within the scope of authorization of the power of attorney. However, the power of attorney still requires the seal of the unit or the signature of the legal representative. This goes back to the argument just now. However, in practice, many company salespeople do not have a power of attorney from the company, because the other party has reason to believe that the salesperson’s actions are on behalf of the company, which of course constitutes apparent agency. His actions can be deemed valid.

Anyway, that’s the truth. More importantly, we still need to pay attention to the actual requirements of the other party. If the other party trusts it, the signature or seal will be legally valid.