legal ground
Article 155 of the Civil Code of People's Republic of China (PRC)
An invalid or revoked civil juristic act is not legally binding from the beginning.
Article 157
After a civil juristic act is invalid, revoked or deemed invalid, the property acquired by the actor as a result of the act shall be returned; If it is impossible or unnecessary to return it, it shall be compensated at a discount. The party at fault shall compensate the other party for the losses thus suffered; If all parties are at fault, they shall bear their respective responsibilities. Where there are other provisions in the law, those provisions shall prevail.