Proprietary estoppel is a legal principle in English law that can arise in certain circumstances where a person has relied on a promise or assurance made by another person about his rights to a particular property, and has acted to his detriment as a result. In such cases, the person who made the promise or assurance may be prevented from denying the other person's right to the property or may be required to compensate them for their loss. To establish promissory estoppel, you must prove the presence of the following elements:
Assurance: a party gives a clear assurance that the other party will acquire a right over property.
Reliance: the other party reasonably relies on the assurance.
Change of position or Detriment: the other party acts substantially to his detriment on the strength of the assurance or he is now in a different position for having relied on the assurance.
Unconscionability: it would be unconscionable to the other party if the party who gives the assurance to go back on his assurance.
For example, if a person is promised by a family member that he will inherit a piece of land, and based on that promise, he invest significant time and money in improving the land, he may be able to claim a right to the land through proprietary estoppel. The following is the analysis of this example using the above framework.
Assurance: your father assures you that he will give you his property.
Reliance: you rely on his assurance which induces you to spend money improving the property.
Change of position or Detriment: after spending money improving the property, you are now less well off and financially in a worse position for having relied on the assurance.
Unconscionability: it would be unconscionable to you if your father gives the property to your brother instead.
You can learn more about this topic with our Property Law (Land Law) notes.