If a man due to his own negligence or lack of reasonable care does not ascertain what he is contracting about, he must blame himself and cannot avoid the contract. Thus, as a rule, a unilateral mistake is not allowed as a defence in avoiding a contract i. e” it has no effect on the contract and the contract remains valid.
Illustrations:
(a) Where the government sold by auction the right of fishery and the plaintiff offered the highest bid thinking that the right was sold for three years, when in fact it was for one year only, he could not avoid the contract because it was his unilateral mistake caused by his own negligence.
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ADVERTISEMENTS:
He ought to have ascertained the tenure of fishery before bidding at the auction (A.A Singh vs Union of India).
(b) X buys rice from Y, by sample under the impression that the rice is old. The rice is, however, new. X cannot avoid the contract. The rule of caveat emptor (let the buyer beware) of the Sale of Goods Act is generally applicable in such cases of unilateral mistake as to quality of subject-matter of a contract, and despite the mistake the contract remains valid.
Contract voidable:
ADVERTISEMENTS:
If the unilateral mistake is caused by fraud or misrepresentation, etc. on the part of the other party, the contract is voidable and can be avoided by the injured party.
Illustration:
A, has a horse with a hole in the hoof 4, so fills it up that the defect cannot be discovered on a reasonable examination. B, purchases the horse under the impression that the horse is sound. Here A, is guilty of fraud and as such on discovery of the defect B can avoid the contract because his unilateral mistake has been caused by 4’s fraud.