Whether an alteration on the rental contract is valid or not depends on the circumstances, as follows:

1. Alterations on the rental contract are valid contracts agreed upon by both parties;

2. The altered content will not be effective without the signature and seal of both parties.

After a dispute arises between the parties to the contract, the main resolution methods are as follows:

1. The first is settlement through negotiation. Negotiation means that after the contract dispute occurs, the parties to the contract resolve the disputed issues in the contract. Negotiations are conducted in which both parties make certain concessions and reach a settlement agreement on the basis that both parties find acceptable;

2. The second type is reconciliation and mediation. Reconciliation refers to the parties negotiating on their own to resolve the issues. Disputes arising from a contract; mediation refers to a method of coordinating the interests of both parties under the auspices of a third party so that both parties can resolve disputes on a voluntary basis; reconciliation and mediation can be conducted outside of litigation, or at a certain point during litigation. Proceed in stages. If the parties are unwilling to reconcile or mediate, or if reconciliation or mediation is unsuccessful, they may apply for arbitration based on the arbitration agreement reached; however, reconciliation and mediation are not necessary procedures for the parties to apply for arbitration or initiate litigation;

3. Thirdly The first is arbitration, which refers to the method in which the parties to a contract submit contract disputes to an arbitration institution in accordance with the arbitration agreement and the arbitration institution makes a ruling. An arbitration institution is an institution established in accordance with legal provisions to adjudicate contract disputes; the awards made by the arbitration institution are legally binding. Arbitration institutions are not judicial organs. Their decision-making procedures are simple and disputes can be resolved quickly. If a party has a contract dispute, they may apply to an arbitration institution for arbitration based on an arbitration agreement reached in advance or afterwards. The parties to a foreign-related contract can not only agree to apply for arbitration to a Chinese arbitration institution, but also agree to apply for arbitration to a foreign arbitration institution;

4. The fourth option is to sue.

In summary, after the contract comes into effect, if the parties have not agreed on quality, price or remuneration, place of performance, etc. or the agreement is unclear, they can reach an agreement to supplement it; if they cannot reach a supplementary agreement, the relevant terms of the contract will apply. Or the trading habits are determined.

Legal basis:

Article 509 of the "People's Republic of China and Civil Code"

The parties shall fully perform their obligations as agreed.

The parties shall abide by the principle of good faith and perform obligations such as notification, assistance, and confidentiality in accordance with the nature, purpose and transaction habits of the contract.

In the process of performing the contract, the parties shall avoid wasting resources, polluting the environment and damaging the ecology.