1, the parties to the contract have corresponding capacity for civil conduct, and the intention is true;

2, the content does not violate the law, does not violate the public order and good customs with legal effect. The contract is invalid if it violates the law and infringes upon the legitimate rights and interests of others.

What are the classifications of contracts?

The classification of contracts is as follows:

1. Bilateral contracts and unilateral contracts. A bilateral contract is a contract in which both parties undertake obligations, and the obligations and rights of both parties are interrelated and mutually causal. A unilateral contract is a contract in which only one party undertakes obligations and the other party only enjoys rights.

2. Paid contracts and unpaid contracts. A paid contract refers to a contract in which one party must pay a certain price to the other party in order to obtain rights, such as buying and selling and reciprocal contracts. A gratuitous contract is a contract in which one party only obtains rights without paying the price.

Legal basis: Article 502 of the Civil Code of People's Republic of China (PRC).

A legally established contract shall come into force upon its establishment, except as otherwise provided by law or agreed by the parties.

In accordance with the provisions of laws and administrative regulations, if the contract should go through the approval procedures, such provisions shall prevail. If the failure to go through the formalities such as approval affects the effectiveness of the contract, it will not affect the performance of the obligation clauses such as approval and the effectiveness of relevant clauses in the contract. If the party that should go through the formalities for approval fails to perform its obligations, the other party may require it to bear the responsibility for violating its obligations.

The modification, assignment and dissolution of a contract shall be subject to the provisions of laws and administrative regulations, and the provisions of the preceding paragraph shall apply and shall be subject to approval.