1. If the person who signed the labor contract is the legal representative of the employer, since his behavior directly represents the behavior of the employer, the legal representative has signed the labor contract, which proves the employer's recognition and consent to this labor contract. Even if the employer does not stamp, the labor contract is valid.
2. If the person who signs the labor contract is not the legal representative of the employer, but other staff members, since these people cannot act directly on behalf of the employer in law, their signature behavior can only bind the employer and make the contract effective if they obtain authorization in advance.