Equitable estoppel is a defensive doctrine preventing one party from taking unfair advantage of another when, through false language or conduct, the person to be estopped has induced another person to act in a certain way, which resulted in the other person being injured in some way. This doctrine is founded on principles of fraud. It prevents one party from taking a different position at trial than s/he did at an earlier time if the other party would be harmed by the change. Generally, the elements that need to be proved are:

There must be a representation or concealment of material facts.
These facts must be known at the time of the representation to the party being estopped.
The party claiming the benefit of the estoppel must not know the truth concerning these facts at the time of the representation.
The representation must be made with the intention or the expectation that it will be acted upon.
The representation must be relied upon and acted upon.
The party acting upon the representation must do so to his or her detriment.
Equitable estoppel is also termed as estoppel by conduct or estoppel in pais.