无效合同（Invalid contract），是指合同虽然已经成立，但因其严重欠缺有效要件，在法律上不按当事人之间的合约赋予其法律效力。

一方以欺诈、胁迫的手段订立合同，损害国家利益；恶意串通，损害国家、集体或者第三人利益；以合法形式掩盖非法目的；损害社会公共利益；违反法律、行政法规的强制性规定。

《合同法》规定有下列情形之一的，合同无效：

（一）一方以欺诈、胁迫的手段订立合同，损害国家利益；

（二）恶意串通，损害国家、集体或者第三人利益；

（三）以合法形式掩盖非法目的；

（四）损害社会公共利益；

（五）违反法律、行政法规的强制性规定。

A contract shall be null and void under any of the following circumstances:

(1) a contract is concluded through the use of fraud or coercion by one party to damage the interests of the State;

(2) malicious collusion is conducted to damage the interests of the State, a collective or a third party;

(3) an illegitimate purpose is concealed under the guise of legitimate acts;

(4) damaging the public interests;

(5) violating the compulsory provisions of laws and administrative regulations.

参考双语例句：

Concerning forced labour, the labour code stipulates that all work must be paid, that a contract will be void if it establishes a wage lower than that paid to another worker in the same enterprise for work of equal effectiveness or sets a wage lower than the legal minimum; if it requires one day of work more than is permitted by the labour code; or if it entails a direct or indirect obligation to buy goods or food from a store, business or place determined by the employer (art. 47).

关于强制劳动问题，《劳工法》规定：所有工作都必须得到报酬并在以下情况下合同无效：合同规定的工资低于付给同企业中从事同效工作的另一个工人的工资，或所定工资低于法定最低标准；合同要求的工作日比《劳工法》规定的多一天；或者会引起一种直接或间接的义务，须从业主所规定的商店、商家或地方购买货物或食品(第 47 条)。

The Provincial High Court considered that, although the judgement appealed against also cited Spanish case law in relation to article 1124 of the Civil Code (Discharge by breach), such case law was along the same lines as article 25 of CISG, which provided that the buyer might declare the contract avoided where the breach was serious and fundamental, without needing to adduce the failure to perform secondary or complementary actions that, not being of vital importance, had not prevented the creditor from obtaining the financial result that had prompted it to conclude the contract.

省高等法院认为，尽管上诉所针对的判决也援引了与《民法》第1124条（因违约而解除合同）有关的西班牙判例法，但这种判例法与《销售公约》第 25 条相一致，其中规定，如果发生严重和根本违反合同，买方可宣布合同无效，而无需引证未能实施后续或补充行为，因为这些行为不是至关重要的，并未妨碍债权人获得促使其缔结合同的财务结果。

This guide outlines some key contract provisions that you need to include in your agreements, important clauses that must not be used in China (because they could be in contravention of the Chinese laws thus rendering the contract void), how to protect confidential information through contracts, and protecting the ownership of new IP created in China).

本指南列举了协议中需要包含的关键合同规定、中国不能使用的重要条款（因为其或与中国法律相抵触，从而导致合同无效）、如何通过合同保护保密信息、以及如何保护在中国新创造的知识产权所有权。