• Common mistake is said to exist when both parties make the same mistake.
• Each party knows the others intention but both are unaware of an underlying fundamental fact.
• This is a mistake as to the existence or ownership of the subject matter.
• Common mistake renders a contract void in two circumstances:
o Cases of res extincta: these are circumstances in which the parties are unaware that the subject matter does not exist. For example in Couturier V. Hastie. In such a case the contract is void. Section 8 of the Sale of Goods Act embody this
q Cases of res sua: these are circumstances in which the person purporting to buy has legal title in the subject matter. As was the case in Bingham V. Bingham.