Legal Definitions - reexamination certificate

A reexamination certificate is an official document issued by the U.S. Patent and Trademark Office (USPTO) at the conclusion of a reexamination process for an existing patent.

Its purpose is to formally update the patent's legal status after a review. This certificate can confirm that the patent's original protected features (known as "claims") are still valid, officially cancel any claims found to be invalid, or incorporate new or amended claims that were determined to be patentable during the reexamination.

Here are some examples illustrating how a reexamination certificate works:

• Example 1: Patent Claims Confirmed

  Imagine a company holds a patent for a unique water purification system. A competitor challenges this patent, arguing that similar technology already existed before the patent was granted. The USPTO conducts a reexamination, thoroughly reviewing the patent against all known prior art. After the review, the USPTO determines that all of the original claims describing the water purification system are indeed novel and non-obvious. A reexamination certificate is then issued, officially confirming that the patent's original claims remain valid and enforceable, effectively strengthening the patent holder's position against the competitor.

• Example 2: Patent Claims Partially Canceled

  An inventor has a patent for a new type of ergonomic office chair, which includes several distinct features (claims), such as a specific lumbar support mechanism and a unique armrest design. During a reexamination requested by a third party, it is discovered that the specific armrest design was actually described in an older, obscure patent that was overlooked during the initial examination. However, the lumbar support mechanism is still found to be entirely new and patentable. The reexamination certificate would then formally cancel the claims related to the armrest design from the inventor's patent, while confirming the continued validity of the claims pertaining to the unique lumbar support.

• Example 3: Amended and New Claims Incorporated

  A software company holds a patent for a novel data compression algorithm. During a reexamination, the USPTO identifies some overlap between certain aspects of the patented algorithm and existing public domain algorithms. To address this, the software company amends its patent claims to more precisely define the unique improvements and specific steps of its algorithm that differentiate it from prior art. They also introduce new claims for a related, previously unpatented feature of their software that leverages this algorithm. Once these amended and new claims are found to be patentable by the USPTO, a reexamination certificate is issued. This certificate officially incorporates these revised and added claims into the patent, clarifying and updating the exact scope of the company's intellectual property protection.