File wrapper estoppel

U.S. patent law
File wrapper estoppel (also called prosecution history estoppel) occurs when an inventor amends its patent application by narrowing the claims during the course of patent prosecution to overcome a rejection. In such a situation, the inventor is precluded or estopped from asserting a broader interpretation after the patent has issued.

This type of estoppel clearly exists in the face of a prior art rejection, but can also exist when the inventor makes representations in a writing that would cause the patent examiner to rely on those representations when it grants a patent based on the application.

Under current law, while file wrapper estoppel does not preclude the use of the doctrine of equivalents, it does substantially limit the scope and application of that doctrine.