Understanding Promissory Estoppel in Relation to Contentious Probate

When someone dies without honouring a promise they made during their lifetime, the people affected often ask whether the law can help. The answer sometimes lies in estoppel, but almost never in the doctrine people first reach for. This guide explains what promissory estoppel actually is, why it rarely helps an inheritance claim, and which doctrine does. It applies to England and Wales.

The short answer

If you were promised an inheritance and the will does not reflect it, promissory estoppel is not your claim. The doctrine you need is proprietary estoppel, and we cover it separately in our guide to proprietary estoppel in contentious probate.

The rest of this article explains why, because the distinction is genuinely important and choosing the wrong framework can sink a good case before it starts.

What is promissory estoppel?

Promissory estoppel is an equitable doctrine that prevents a party from going back on a clear promise not to enforce their strict legal rights, where the other party has relied on that promise and it would be inequitable to allow the promisor to resile.

It developed out of Hughes v Metropolitan Railway (1877) 2 App Cas 439 and was restated in the well-known case of Central London Property Trust Ltd v High Trees House Ltd [1947] KB 130, where a landlord who had agreed to accept reduced rent during the war was held to that agreement for the period it covered.

The elements

For promissory estoppel to operate, the following must be present:

• An existing legal relationship between the parties. This is the defining requirement and the one most often left out. Promissory estoppel modifies or suspends rights arising under a relationship that already exists, typically a contract. It does not operate between strangers, and it does not create a relationship where none existed.
• A clear and unambiguous promise not to enforce those strict rights, specific enough for the other party to understand what was being given up.
• Reliance. The other party must have relied on the promise, acting or refraining from acting as a result.
• Inequity. It must be inequitable, in all the circumstances, to allow the promisor to go back on the promise. In practice this usually means the promisee changed their position, though whether strict detriment is required for promissory estoppel remains unsettled in English law.

The burden of establishing the estoppel lies on the party asserting it, on the balance of probabilities.

What it does to the right: suspension, not extinction

Promissory estoppel is generally suspensory. It holds the promisor to their promise for the period it covers, but the strict rights may be resumed on reasonable notice for the future, as in Tool Metal Manufacturing Co Ltd v Tungsten Electric Co Ltd [1955] 1 WLR 761. Rights are extinguished altogether only where resuming them would itself be inequitable.

This is a second reason the doctrine sits awkwardly with inheritance disputes. Suspending a right temporarily is not the same as transferring an interest in a farm.

A shield, not a sword

This is the single most important limitation. Promissory estoppel cannot found a freestanding claim. It operates defensively: a party being sued can raise it to resist enforcement of a right the other side promised not to enforce, but cannot use it to sue someone who broke a promise.

The principle was settled by the Court of Appeal in Combe v Combe [1951] 2 KB 215, which confirmed that promissory estoppel does not create new causes of action where none existed before. It remains good law and was affirmed at Court of Appeal level in Baird Textile Holdings Ltd v Marks & Spencer plc [2001] EWCA Civ 274.

Where promissory estoppel does arise in contentious probate

There is a real but narrow role for it, and it is defensive.

Suppose the deceased lent money to a friend and later told them, clearly, not to worry about repaying it, and the friend arranged their affairs accordingly. If the executor now seeks to call in that loan as an asset of the estate, the friend may raise promissory estoppel as a defence. The same analysis can apply to a promise not to enforce a guarantee, or not to insist on a contractual term.

The common thread is that there was already a legal relationship, the deceased promised not to enforce a right arising under it, and the estate is now trying to enforce it anyway. That is promissory estoppel doing exactly the work it was designed for.

What it cannot do is turn a promise of an inheritance into a claim against the estate.

Proprietary estoppel: the doctrine that actually founds inheritance claims

Where someone was led to believe they would receive an interest in property and acted on that belief to their detriment, the relevant doctrine is proprietary estoppel. Unlike promissory estoppel, it can be used as a cause of action in its own right, and it does not require any pre-existing legal relationship.

Its elements are an assurance, reliance on that assurance, detriment suffered as a result, and unconscionability in allowing the assurance to be resiled from. Gillett v Holt [2001] Ch 210 is the case usually cited for the point that these elements are not to be treated as watertight compartments but considered in the round.

It is the doctrine behind the farming cases, where a family member works for years for little pay on the strength of a promise to inherit the land, as in Thorner v Major [2009] UKHL 18, and behind claims by long-serving carers, as in Jennings v Rice [2002] EWCA Civ 159.

The remedy is discretionary, not automatic

It is worth being clear that succeeding in proprietary estoppel does not entitle you to whatever you were promised. Since Guest v Guest [2022] UKSC 27, where the Supreme Court allowed the parents’ appeal in part by a majority and substituted a less generous award than the courts below had given, the remedy is directed at avoiding an unconscionable outcome. The expectation is the starting point rather than the entitlement, and where relief is given early a discount for accelerated receipt may apply.

Our guide to proprietary estoppel in contentious probate covers the elements, the case law and the remedies in full. If you believe you were promised an inheritance, that is the page to read next.

Promissory and proprietary estoppel side by side

The two are frequently confused, so it is worth setting out the differences plainly.

• Relationship. Promissory estoppel requires an existing legal relationship between the parties. Proprietary estoppel does not.
• Subject matter. Promissory estoppel concerns rights under that relationship, usually contractual. Proprietary estoppel concerns an interest in property or land.
• Use. Promissory estoppel is a defence only. Proprietary estoppel can found a claim.
• Effect. Promissory estoppel generally suspends rights, which may be resumed on notice. Proprietary estoppel can create a new interest in property or produce a monetary award in its place.

Both aim at preventing unfairness, but they are not interchangeable, and describing promissory estoppel as the “broader” doctrine inverts the practical position. It is the narrower one in the respect that matters most.

Other routes worth considering

Estoppel is not the only answer where a promise has gone unfulfilled.

A claim under the Inheritance (Provision for Family and Dependants) Act 1975 may be available where you fall within one of the categories of eligible applicant and the will or intestacy fails to make reasonable financial provision for you. Our guides to making an Inheritance Act claim and claims by cohabitants set out how that works, and successful and unsuccessful claims gives a sense of how the courts approach them.

Where the concern is the validity of the will itself rather than a promise made outside it, see contesting a will.

There may also be a straightforward contractual claim, or a claim in restitution, depending on what was said and what was done in reliance.

Acting quickly, and why it matters

If you think a claim may exist, take advice promptly. There are two distinct reasons.

The first is evidential. Estoppel claims turn on what was said, often years ago and often without documents. Witnesses’ memories fade and people die. Delay costs cases.

The second is legal. There is no single statutory limitation period covering all estoppel claims, but equitable relief can be barred by laches, the doctrine under which unreasonable delay combined with prejudice to the other side defeats a claim, and by acquiescence.

Where an Inheritance Act claim is also in play, there is a time limit and it is short: six months from the date on which representation was first taken out. Note that this runs from the grant of representation, which includes letters of administration on an intestacy, not only from a grant of probate. The court has a discretion to give permission for a late claim, so a missed deadline is not necessarily fatal, but permission is not given as a matter of course and you should not rely on it. Our guide to Inheritance Act time limits explains how the court approaches late applications.

If you need to stop a grant issuing while you investigate, or to be told when one is issued, see the probate standing search. To obtain the will itself, see how to get a copy of a will and requesting the original will from a solicitor.

How a contentious probate solicitor helps

The first task is diagnostic: working out which doctrine, if any, fits the facts. Getting that wrong is the most common reason a meritorious case fails, and it is not something to decide from a web page.

From there, a solicitor will help assemble the evidence, which in these cases usually means written communications, witness statements from people who heard the promise, financial records showing how you changed your position, and any diaries or informal notes. They will then advise on whether to negotiate, mediate or issue proceedings. Most estoppel claims settle, and mediation is well suited to them.

You can find a contentious probate solicitor through The Probate Network, and our guide to contentious probate explains what the process involves.

Frequently asked questions

Can I use promissory estoppel to claim an inheritance that was promised to me?

No, not on its own. Promissory estoppel operates only as a defence and cannot create a new cause of action, and it requires an existing legal relationship between the parties that it modifies. If you were promised an inheritance and the will does not reflect it, the doctrine you need is proprietary estoppel, which can found a claim in its own right and does not require any prior relationship.

What is the difference between promissory and proprietary estoppel?

Promissory estoppel prevents someone enforcing strict legal rights under an existing relationship after promising not to. It works as a shield only and generally suspends rights rather than extinguishing them. Proprietary estoppel concerns an interest in property, arises where an assurance was relied on to the claimant’s detriment, needs no pre-existing relationship, and can be used to bring a claim. In inheritance disputes it is almost always proprietary estoppel that matters.

Is promissory estoppel ever relevant in a probate dispute?

Yes, but defensively. If the deceased promised not to enforce a debt, a guarantee or a contractual term, and the executor now tries to enforce it as an asset of the estate, the other party may raise promissory estoppel as a defence. That is its proper role here. It is not a route to a share of the estate.

What do I have to prove, and who has to prove it?

The party asserting the estoppel must prove it, on the balance of probabilities. For promissory estoppel that means the existing relationship, the clear promise, reliance on it, and that it would be inequitable to allow the promisor to go back on it. For proprietary estoppel it means an assurance, reliance, detriment and unconscionability, considered in the round rather than as separate hurdles.

How long do I have to bring an estoppel claim?

There is no single statutory limit covering all estoppel claims, but equitable relief can be defeated by laches, meaning unreasonable delay that prejudices the other side, and by acquiescence. Where a claim under the Inheritance (Provision for Family and Dependants) Act 1975 is also involved, the period is six months from the date representation was first taken out, which includes letters of administration on an intestacy. The court can give permission for a late claim, but you should not count on it. Take advice as early as you can.

If I win a proprietary estoppel claim, do I get what I was promised?

Not necessarily. The remedy is discretionary and aimed at avoiding an unconscionable result rather than enforcing the promise as if it were a contract. Since Guest v Guest in 2022, the expectation is the starting point for the court’s assessment rather than a guaranteed entitlement, and an award made earlier than the promise would have matured may be discounted to reflect that.

This article is for general guidance only and applies to England and Wales. It does not constitute legal, tax or financial advice. The law can change and every case turns on its own facts. For advice on your own circumstances, speak to a qualified professional. You can book a free legal consultation through The Probate Network.