Whether the contract is valid or not can be divided into the following situations: 1. After the signing of this contract, if either party takes illegal measures to control others or steals this contract to modify or forge the contract, the modified part of the contract will be invalid and the original contract content will be maintained; After the contract is signed, if either party wants to modify the contract, it must inform the other party. After both parties reach an agreement through consultation, they shall re-sign the contract or modify or supplement the corresponding terms of the original contract, and affix the official seals (personal handprints) of both parties at the modified place. If only a verbal commitment is made, but the contract is not modified, or there is no seal (handprint) in the changed place, it will be deemed invalid and the original contents of the contract will continue to take effect.