Estoppel
ɪˈstɒpəl / uh-STOP-uhl
A legal principle that prevents a person from contradicting a position they previously took, where another party reasonably relied on that position to their detriment.
Origin
Middle English, from Old French "estouper" meaning "to plug" or "to stop up". Originally from Latin "stuppa" (tow, hemp fibre used as plugging material). The legal sense developed from the idea of "stopping" someone from contradicting themselves.
Definition
Estoppel is one of the foundational equitable doctrines in Irish law. It operates to prevent unfairness — specifically, where one party has made a representation, conducted themselves in a particular way, or agreed to certain facts, and the other party has acted on that basis to their disadvantage.
The doctrine has several distinct forms in Irish law:
Promissory estoppel applies where one party makes a clear promise intending to be relied upon, and the other party does in fact rely on it. The party making the promise is then “estopped” from going back on it, even if the original promise wouldn’t have been legally enforceable as a contract.
Proprietary estoppel arises in property matters — for example, where a landowner allows another person to act as if they had rights over the land, and that person spends money or otherwise relies on this. The landowner may be prevented from later denying those rights.
Estoppel by representation prevents a party from denying the truth of a statement they previously made, where the other party relied on it.
In tenancy and property disputes, estoppel often arises around informal arrangements — such as where a landlord repeatedly accepts late rent without complaint, or where a property owner allows a neighbour to use part of their land for years without objection.
Usage examples
In a tenancy dispute:
If a landlord repeatedly accepts late rent without complaint over several months, they may be estopped from later treating that late payment as grounds for terminating the tenancy.
In a property dispute:
Where a landowner stands by while a neighbour builds a fence on what is actually their property, then waits years to complain, the doctrine of proprietary estoppel may prevent them from demanding removal.
In contract law:
Two parties agree informally to a contract variation. One party spends money on the strength of that agreement. Even if the variation didn't meet the formal requirements of contract law, the other party may be estopped from denying the variation.
Synonyms
- Estoppel by representation
- Promissory estoppel
- Proprietary estoppel
- Equitable estoppel
- Collateral estoppel
Antonyms
- Reservation of rights
- Non-waiver
- Repudiation
- Revocation
- Denial / traverse in pleadings
Sources
- Central London Property Trust Ltd v High Trees House Ltd [1947] KB 130
- Re Basham [1986] 1 WLR 1498 (proprietary estoppel)
- Doran v Thompson Ltd [1978] IR 223 (Irish application of promissory estoppel)
Important: Definitions on Legals.ie are general information for educational purposes only and do not constitute legal advice. For specific situations, consult a qualified solicitor.