Res Judicata – 

           Section 11 of the Civil Procedure Code, 1908 relates to the principle of res judicata. Res Judicata which meansmatter already adjudged upon cannot be re-agitated again, or a matter in which judgment is already pronounced. The Doctrine Res Judicata is based upon the principle that one should not be vexed twice for the same cause and there should be finality of litigation. It helps to prevent endless litigations.  It is based on public policy.

Estoppel – 

             Indian Evidence Act 1872, Part III Chapter VII containing Sections 115 to Section 117 lay down the provisions relating to the Doctrine of Estoppel. Section 116 of the said Act deals with estoppel of tenant and of licensee of persons in possession. According to Section 115 of the Indian Evidence Act, “When one person has by his declaration, act or omission, intentionally caused or permitted another person to believe a thing to be true and to act upon such belief, neither he nor his representative shall be allowed, in any suit or proceeding between himself and such person or his representative, to deny the truth of that thing.”

Distinction/Difference Between Res Judicata and Estoppel – 

See some Major Differences between Res Judicata and Estoppel.

No Res Judicata Estoppel
1) As we all know the doctrine of Res Judicata results from the decision of the court. On the other hand Estoppel results from the acts of the parties.
2) It proceeds on the ground of public policy Estoppels  proceeds upon the doctrine of equity
3) Res Judicata prevent a man arriving the same thing twice in successive litigation On the other hand estoppel prevents him from saying one thing at one time and the opposite at another.
4) The theory of res judicata is to presume conclusively the truth of the former decision. The rule of Estoppel prevents a person from setting up what he calls the truth.
5) The Doctrine of Res Judicata outs the jurisdiction of the Court to try the case. On the other hand Estoppel is only a rule of evidence.