Contract law
Formation
Capacity Offer and acceptance Meeting of the minds2 Abstraction principle4,5 Posting rule1 Mirror image rule Invitation to treat Firm offer Consideration1,4 Implication-in-fact Collateral contract
Defences
Misrepresentation Mistake Threats and unequal bargaining power Illegality and public policy Unconscionability Culpa in contrahendo2 Force majeure Frustration of purpose Impossibility Impracticability Hardship Set-off Illusory promise1 Statute of frauds1 Non est factum1 Unclean hands1 Accord and satisfaction1 Exculpatory clause
Interpretation
Parol evidence3 Contract of adhesion Integration clause Contra proferentem UNIDROIT Principles of International Commercial Contracts
Dispute resolution
Choice of law clause Forum selection clause Hague Choice of Court Convention Arbitration New York Convention UNCITRAL Model Law on International Commercial Arbitration Mediation Singapore Mediation Convention Enforcement of foreign judgments Hague Judgments Convention
Rights of third parties
Privity of contract1 Assignment Delegation Novation Third-party beneficiary
Breach of contract
Anticipatory repudiation Cover Exclusion clause Efficient breach Deviation Fundamental breach
Remedies
Specific performance3 Money damages Liquidated, stipulated, or penal damages3 Rescission
Quasi-contractual obligations
Promissory estoppel1 Quantum meruit1 Unjust enrichment Restitution Negotiorum gestio2
Duties of parties
Duty of honest contractual performance (or doctrine of abuse of rights)6 Duty of good faith (also implied covenant of good faith and fair dealing or duty to negotiate in good faith)7 Contract A and Contract B6
Related areas of law
Conflict of laws Commercial law
By jurisdiction
Australia Canada China (mainland) Ireland India Saudi Arabia United Kingdom England and Wales Scotland United States
Other law areas
Tort law Property law Wills, trusts, and estates Criminal law Evidence
Notes
1 Specific to common law jurisdictions 2 Specific to civil and mixed law jurisdictions 3 Historically restricted in common law jurisdictions but generally accepted elsewhere; availability varies between contemporary common law jurisdictions 4 Specific to the German Bürgerliches Gesetzbuch and other civil codes based on the pandectist tradition 5 Explicitly rejected by the UNIDROIT Principles of International Commercial Contracts 6 Specific to Canadian contract law both in Québec and in the country's common law provinces 7 Specific to civil law jurisdictions, the American Uniform Commercial Code, and Canadian jurisprudence in both Québec and the common law provinces pertaining to contractual and pre-contractual negotiation
v t e

An illegal agreement under the common law of contract, is one that the court will not enforce because the purpose of the agreement is to achieve an illegal end. The illegal end must result from performance of the contract itself. The classic example of such an agreement is a contract for murder.

The illegality of a contract depends on (1) the law of the country governing the contract, and (2) the law of the place of performance. Different rules will apply depending on the law of the relevant country(ies).

However, a contract that requires only legal performance on the part of each party, such as the sale of packs of cards to a known gambler, where gambling is illegal, will nonetheless be enforceable. A contract directly linked to the gambling act itself, such as paying off gambling debts (see proximate cause), however, will not meet the legal standards of enforceability. Therefore, an employment contract between a blackjack dealer and a speakeasy manager, is an example of an illegal agreement and the employee has no valid claim to his anticipated wages if gambling is illegal under that jurisdiction.

In Bovard v. American Horse Enterprises (1988),^[1] the California Court of Appeal for the Third District refused to enforce a contract for payment of promissory notes used for the purchase of a company that manufactured drug paraphernalia. Although the items sold were not actually illegal, the court refused to enforce the contract for public policy concerns.

In Canada, one cited case of lack of enforceability based on illegality is Royal Bank of Canada v. Newell (1997 NSCA 196), in which a woman forged her husband's signature on 40 cheques, totalling over $58,000. To protect her from prosecution, her husband signed a letter of intent prepared by the bank in which he agreed to assume "all liability and responsibility" for the forged cheques. However, the agreement was unenforceable, and was struck down by the courts, because of its essential goal, which was to "stifle a criminal prosecution". Because of the contract's illegality, and as a result voided status, the bank was forced to return the payments made by the husband.

Contracts in restraint of trade are a variety of illegal contracts and generally will not be enforced unless they are reasonable in the interests of the contracting parties and the public.

Contracts in restraint of trade if proved to be reasonable can be enforced. When restraint is placed on an ex-employee, the court will consider the geographical limits, what the employee knows and the extent of the duration. Restraint imposed on a vendor of business must be reasonable and is binding if there is a genuine seal of goodwill. Under common law, contracts to fix prices are legal. Sole supplier ("solus") agreements are legal if reasonable. Contracts which contravene public policy are void.