A transaction made under the influence of a misapprehension having a substantial significance may be declared invalid by a court on suit by the party who acted under the influence of the mistake.

A misapprehension has a substantial significance if it is with respect to the nature of a transaction or qualities of its subject that significantly reduce the possibility of its normal use.

A misapprehension concerning the motives of the transaction does not have a substantial significance.

If a transaction is declared invalid as made under the influence of a misapprehension take, each of the parties has the duty to return to the other everything received under the transaction and in case of the impossibility of physically returning what was received (including when what was received consisted of the use of property, work done, or services provided) to compensate for its value in money, unless other consequences of the invalidity of the transaction are provided by a statute.

In addition, the party on whose suit the transaction was declared invalid shall have the right to claim from the other party compensation for the actual damage caused to it if it proves that the misapprehension take arose due to the fault of the other party. If this is not proved, the party, on whose suit the transaction was declared invalid, shall be obligated to compensate the other party on its demand for the actual damage caused to it, even if the misapprehension take arose due to circumstances not depending upon the misapprehended party.

Actual damage means the expenses that the person whose right was violated made or must make to reinstate the right that was violated, the loss of or injury to his property.

The source: iravaban.net