Your Cart

Promissory Estoppel vs Proprietary Estoppel

Promissory estoppel and proprietary estoppel are both legal doctrines that prevent a person from going back on their word under certain conditions, but they apply in different contexts and have different requirements.

Promissory Estoppel is generally used in the context of contract law. This doctrine comes into play when one party makes a promise to another party, who then relies on that promise to their detriment. The essential elements of promissory estoppel are: a clear and unambiguous promise, reasonable and detrimental reliance by the promisee on the promise, and an injustice that can only be avoided by enforcing the promise. For example, suppose a landlord promises a tenant that the tenant can live rent-free for a year if they improve the property. The tenant, relying on this promise, spends money on improvements. Even though there was no formal contract, the landlord may be estopped (prevented) from charging rent, as it would be unjust to allow the landlord to renege on the promise after the tenant has incurred expenses based on it.

Proprietary Estoppel is used in the context of property rights. This doctrine applies when someone is led to believe that they will acquire rights to a property, they rely on this belief to their detriment, and it would be unjust to deny them some form of right over the property. For example, consider a situation where an elderly parent tells their child that they will inherit the family home, and in reliance on this, the child spends years caring for the parent and investing in the upkeep of the home. If the parent later decides to will the home to someone else, proprietary estoppel could be invoked to give the child some rights to the property, because the child acted to their detriment based on the parent's assurances.

Both doctrines serve to enforce fairness and prevent parties from acting against their promises or assurances when others have relied on those to their detriment. However, the key distinction lies in the nature of the promise: promissory estoppel is about promises in general that lead to financial or other detriments, while proprietary estoppel specifically relates to promises or assurances about rights to use or own property.

Check out our high-performance law notes for Contract Law and Property Law now.

Trusted by thousands of law students worldwide

Where are our students from?

Yale University

Council of Europe

Baker Mckenzie 

University of Chicago

Columbia University

New York University

University of Michigan 


University College London (UCL)

London School of Economics (LSE)

King’s College London (KCL)

University of London

University of Manchester

University of Zurich

University of York

Brandeis University

University of Exeter

University of Sheffield

Boston University

University of Washington

University of Leeds

University of Law

Royal Holloway, University of London 

Birkbeck, University of London

SOAS, University of London

University of Kent

University of Hull

Queen’s University Belfast

Toronto Metropolitan University

Hong Kong University of Science and Technology

University of Buckingham

Your perfect companion for open-book and closed-book exams

Diagrams and Charts

Our carefully designed diagrams and charts will guide you through complex legal issues.

Clear and Succinct Definitions

Key concepts are concisely defined to help you understand legal topics quickly.

Statutory Provisions

Statutory provisions are provided side by side with legal concepts to help you swiftly locate the relevant legislation.

Case Summaries

We have summarised important cases for you so that you don't need to read long and boring cases.

Rules and Exceptions

Rules and exceptions are clearly listed so that you know when a rule applies and when it doesn't.


Legal terms and key concepts are explained at the beginning of each chapter to help you learn efficiently.

Case Law

Case law is provided side by side with legal concepts so that you know how legal principles and precedents were established.

Law Essay Guide

You will learn essential law exam skills and essay writing techniques that are not taught in class.

Problem Question Guide

We will show you how to answer problem questions step by step to achieve first-class results.

Structured Explanations

Complex legal concepts are broken down into concise and digestible bullet point explanations.

Legal Research

You will learn legal research techniques with our study guide and become a proficient legal researcher.


All essential concepts, principles, and case law are included so that you can answer exam questions quickly.