What is main difference between \’Estoppel\’ and \’Res Judicata\’?

It has been said that the doctrine of Res Judicata is one kind of estoppel. Before few years it was recognized as “Estoppel by Judgment\” or “Estoppel by records\”. Both the doctrines can define in single sentence: estoppel means \”once admitted cannot be denied\” and Res-judicata means “once decided cannot be re-decide\”. For the first time the rule of Estoppel was laid down in the well-known case of Pickard v/s. Sears in 1832. In that case their Lordship had observed the principle of Estoppel that …….. Where one by his words or conduct willfully causes another to believe in the existence of a certain state of things and induces him to act on that behalf so as to alter his own previous position, the former is concluded from averring against the later a different state of things as existing at the same time.

From one angle the doctrine of Res judicata seems to be a branch of the law of estoppel. Hon\’ble Allahabad High Court, Madras High Court and Patna High Court have already decided that Res Judicata is a branch of estoppel. (A.I.R. 1960 Mad. 377, AIR. 1939 Pat. 633, AIR. 1950 All. 225). While from other angle it seems to be different. Hon\’ble Calcutta High Court, Hon\’ble Patna High Court and Hon\’ble Madras High Court [AIR 1942 Cal. 93, AIR 1922 Pat. 63, AIR 1947 Mad. 5] have held that the Res Judicata results from a decision of a Court and estoppel results from the acts of parties themselves. The Res Judicata proceeds on the ground of public policy while the rule of estoppel proceeds upon the doctrine of equity,

The doctrine of Res Judicata no doubt resembles the doctrine of estoppel in some respect, but the following are material differences between two. The main distinction between them is the doctrine of res judicata differs from estoppel chiefly in not resulting from an act of party himself but from a decision of the court. In other words, Res judicata results from a decision of the court and estoppel flows from the acts of parties.

Other important things are that, Res judicata ousts the jurisdiction of the court while estoppel does not affect except to shut the mouth of a party. The rule of Res judicata is based on public policy, viz. that there should be an end to litigation, estoppel on other hand proceeds upon the doctrine of equity, that he who, by his conduct, has induced another to alter his position to his disadvantage, cannot turn round and take advantage of such alteration the other\’s position. In other words, while Res judicata bars multiplicity of suits.

Res judicata prohibits a man averring the same thing twice in successive litigation, while estoppel prevents him from saying one thing at one time and the opposite at another.

The rule of Res judicata presumes conclusively the truth of the decision in the former suit, on other hand, the rule of estoppel prevents a party from denying what he had once called the truth.

[As per Sita Ram V/s. Amir Begam – ILR 1986 ALL 324].