Do typographical and other errors in contracts impact the enforceability and validity of a contract? In this article, we explain whether and how errors can affect a contract.
Author: Farrah Motley, Legal Principal of Prosper Law.
If there is a typographical error in a contract then, unless the error is a common mistake, the Court will generally read the contract as a whole, and as if the typographical error did not exist.
Other errors in contracts can be broken down into four categories:
Non est factum
Common mistake and contract law
A common mistake occurs when all the parties to a contract are mistaken about a fundamental fact relating to the contract. If all parties are mistaken about the same fact then the contract may be void or voidable.
Below are some examples of case law where the parties have been held to be commonly mistaken and the contract has therefore been void or voidable:
McRae v Commonwealth Disposals Commission (1951) 84 CLR 377
It was held that only in circumstances where both parties had actual knowledge of a fact, rather than reliance on the other party, will a common mistake occur.
Bell v Lever Brothers Ltd  AC 161
A contract will only be void or voidable for common mistake if the quality of the subject matter is fundamentally or essentially different from what was contracted for.
Pukallus v Cameron (1982) 180 CLR 447
Only if there is a mistake common to both parties under a written document and the intention of both parties is different from what is in the written document, then a contract may be void or voidable.
Mutual mistake and contract law
A mutual mistake happens when both parties are mistaken, but they are mistaken about different things. A mutual mistake doesn't happen often.
Where a mutual mistake exists, the relevant agreement may be unenforceable anyway because it may be too vague or uncertain.
Unilateral mistake and contract law
A unilateral mistake happens when one party is mistaken about an aspect of the contract but the other party is not.
Generally, the issue of a unilateral mistake will arise when there is some improper or misleading and deceptive conduct on the part of the unmistaken party that is seeking to maintain the enforceability of the contract.
If a unilateral mistake occurs, the mistaken party may seek to rescind the contract or rectify the mistake.
Non est factum and contract law
Generally, parties are bound by the documents they sign, whether or not they have read or understood them. However, under contract law principles, if a party can prove that they did not understand the nature of the document they signed (known as a plea of ‘non est factum’ (it is not my deed)), the contract may be unenforceable.
The reliance on the principle of non est factum may be less common with the advent of consumer protection laws, which render void unfair terms in consumer contracts in certain circumstances.