Duress in the context of contract law is a common law defence, and if you are successful in proving that the contract is vitiated by duress, you can rescind the contract, since it is then voidable.

Duress in contract law (in Australia at least) falls into two broad categories:

* Physical duress, and
* Economic duress

Physical duress

Duress to the person

In Barton v. Armstrong [1976] AC 104, a decision of the Privy Council, Armstrong threatened to kill Barton if he did not sign a contract, which was set aside due to duress to the person. An innocent party wishing to set aside a contract for duress to the person need only to prove that the threat was made and that it was a reason for entry into the contract; the onus of proof then shifts to the other party to prove that the threat had no effect in causing the party to enter into the contract.

Duress to goods

In such cases, one party refuses to release the goods belonging to the other party until the other party enters into a contract with them. For example, in Hawker Pacific Pty Ltd v Helicopter Charter Pty Ltd (1991) 22 NSWLR 298, the contract was set aside after Hawker Pacific's threats to withhold the helicopter from the plaintiff unless further payments were made for repairing a botched paint job.
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Economic duress

Although hard bargaining occurs legitimately in commercial situations, there is a point where it becomes economic duress. Putting aside issues of consideration, this often involves one party threatening to breach an existing contract between the two parties unless the innocent party agrees to enter into another contract. The contract is voidable if the innocent party can prove that it had no other practical choice (as opposed to legal choice) but to agree to the contract.