Estoppel is the doctrine that prevents a party from acting in a certain way because it is not equitable to do so. The concept of estoppel is applied in many areas of law.
Promissory estoppel was developed by Lord Denning in Central London Property Trust Ltd. v. High Trees House Ltd. [1947] K.B. 130. In this case High Trees House Ltd obtained the tenancy of a block of flats in 1937 for a ground rent of £2500 per year. Unfortunately the luftwaffe played havoc with occupancy rates in central London after the outbreak of WW2. In January 1940 the plaintiff wrote to the High Trees confirming a reduction in rent to £1250. In September 1945 the receiver of the plaintiff company wrote saying that the rent must be paid at the full amount and demanding arrears. HELD: Full rent was payable from the time that the flats became fully occuppied in early 1945. No arrears before that time could be claimed. I.e. claims for full rent arrears before early 1945 were estopped.
Note that previously under English law, a promise to accept part payment in satisfaction of a debt is not enforcable. For example, a mechanic quotes £300 to fix a car, and does so. The owner of the car pleads that he can only afford £250. The mechanic accepts the £250. There is nothing to stop the mechanic from persuing the remaining payment of £50 at a later time. Applying this principle to High Trees the argeement to accept a lower rent is an acceptance of part payment so there was nothing to stop the plaintiff pursuing the full rent in arrears at a later date. The agreement to accept the lower rent was a promise unsuppported by consideration and so not binding.
Promissory estoppel requires (1) an unequivocal promise by words or conduct, (2) a change in position of the promisee as a result of the promise (not necessarily to anyone's detriment), (3) inequity if the promisor was to go back on the promise. Estoppel is 'a shield not a sword' - it cannot be used as the basis of an action on it's own. It also does not extinguish rights. In High Trees the plaintiff company was able to restore payment of full rent (although estopped back rent was lost) from early 1945, but probably could have could have restored full rent at any time after the initial promise provided a suitable period of notice had been given.
Estoppel is a equitable (as opposed to common law) construct and is therefore discretionary. In the case of D & C Builders v Rees the courts refused to recognise a promise to accept a part payment of £300 on a debt of £482 on the basis that it was extracted by duress.
The American Law Institute included the principle of estoppel into § 90 of the 'Restatement of Contracts', stating:
An example of promissory estoppel in the construction of a building: A construction company puts together the estimates of a number of subcontractors and quotes its client a price. The client accepts, and construction begins. However, thereafter one of the subcontractors drastically raises the price above its original estimate. Because of this change, the construction company cannot profit from the building. A court would be likely to give the construction company promissory estoppel, which would allow them to pay what the subcontractor originally estimated rather than the new, higher price.
Note, in some common law jurisdictions if when you had approached the owner and said indicated that you wanted to purchase one of those radios and he had said, 'sold' you may be able to argue that the contract had been created then, even if you had to go get the money. But under the classical idea of consideration until you paid him the contract would not have been concluded.Collateral Estoppel
Collateral estoppel prevents a party to a lawsuit from raising a fact or issue which was already decided against that party in another lawsuit. Equitable Estoppel
Equitable estoppel prevents one party from taking a different position at trial than they did at an earlier time if another party would be harmed by the change position.Proprietary Estoppel
Proprietary Estoppel in English and Welsh Law
Proprietary estoppel arises when one party purports to give but fails to effectively convey, or promises to give land or an interest in land, to another party knowing that party will expend money or otherwise act to his detriment in reliance of the supposed or promised gift. See Dillwyn v Llwellyn (1862) 4 De G.F.& J. 517 C.A. in Chancery. In this case a father presented property to the son who took possession and expended a large sum of money on the house and otherwise improved the property. The father never conveyed the property. After his death the son, claiming to the equitable owner, obtained an order that the trustees convey the land to him. See also Inwards v Baker [1965] 2 Q.B. 29, C.A.Promissory Estoppel
Promissory Estoppel is the doctrine that prevents a party from acting in a certian way because the first party promised not to, and the second party relied on that promise and acted upon it. Promissory Estoppel in English and Welsh Law
In English law, a promise made without consideration is generally not enforcable. For example, a car saleman promises not to sell a car over the weekend, but does so. The promise cannot be enforced. If however, the car salesman accepts 1 pence in 'consideration' for the promise, the promise is binding and enforcable in court. Estoppel is one of the exceptions to this rule.Promissory Estoppel in American Law
In the many juridictions of the United States, promisory estopple is generally an alternative to consideration as a basis for enforcing a promise. It is also sometimes referred to as deterimental reliance.
A simple example: you go to a store and see a sign that the price of one of store owners product's a radio, is $10. You speak with the owner and tell him you will get the money and come back later that day to purchase it, there is no discussion of price. He says that when he returns he will be happy to deal with you as he deals with all his customers, but that if sells all the radios (he has three) then he will not be able to help you. You go sell your watch for $10 which was really worth $15 but since you wanted the money right away you could not wait for the best price and you sold it to someone who you knew would take $10. When you return the sign says $11, and the owner tells you he has changed the price. In equity he may be estopped from his conduct. You relied upon his representation that he would sell you the radio when you came back the same day with the money; you had sold your watch at a price lower than the market price and thus you have acted to your detriment. (Note if your watch was worth $10 and you received fair price there would not be any detriment on your part).