If the company changes, that is, the contract subject changes, the contract can be changed or re concluded through negotiation. The change of the contract is a partial change of the contract content, a non fundamental change of the contract. The change of the contract is only a modification and supplement to the content of the original contract relationship, not a complete change of the contract content. If the contents of the contract have all changed, it has actually led to the extinction of the original contractual relationship, the emergence of a new contract, and the content of the modification and supplement to the original contractual relationship is limited to non element content, such as the increase or decrease of the subject amount, the place of performance, the time of performance, the price and the change of the settlement method. In the case of non fundamental changes, the changed contractual relationship and the original contractual relationship remain unchanged in nature and belong to the same legal relationship, which is called contract renewal.
 Legal basis
 Article 543 of the Civil Code of the People's Republic of China [Change of contract by agreement] The parties may change the contract if they reach consensus through consultation.