Difference between Estoppel and Waiver are as follows:
Estoppel and waiver are entirely different. Estoppel is not a cause of action. It may, if established, assist a plaintiff in enforcing a cause of action, by preventing the defendant from denying the existence of some fact essential to establish the cause of action. It is a rule of evidence which comes into operation if (a) a statement of the existence of a fact has been made by the defendant (or his authorised agent) to the plaintiff or someone on his behalf, (b) with the intention that the plaintiff should act upon the faith of the statement, and (c) the plaintiff does act upon the faith of the statement.
On the other hand, waiver is contractual, and may constitute a cause of action; it is an agreement to release or not to assert a right. Thus, if an agent with an authority to make such an agreement on behalf of the principal agrees to waive his principal’s right, then (subject to any other question such as consideration), the principal will be bound by the contract, not by estoppel. There is no such thing as estoppel by waiver. (Dawason’s Bank Ltd. v Nippon Menkwa Kabushiki Kaisha, 62 I.A. 100)
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