Unilateral modification of the contract without authorization is invalid. Unilateral modification or tampering with the contract will not have legal effect on the original contract, and the modification is invalid. If the malicious modification causes losses, it may bear civil tort liability. And the other party may refuse to perform, and may also require the other party to bear the liability for breach of contract. According to the law, the change of the contract must be agreed by both parties.
[Legal Basis]
In Article 543 of the Civil Code, the parties may amend the contract if they reach consensus through consultation.
