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Requesting reexamination of an issued patent

Patent holders have numerous rights, including the right to issue licenses for authorized use and the right to prohibit others from using material without permission.

However, circumstances can change during the years when a patent is in place. People discover products or correspondence that could suggest the existence of prior art, which is evidence that patented material was already known. In these cases, an inventor or third party may request an ex-parte reexamination (EPX).

Purpose of EPX

The purpose of reexamination is to determine patentability based on discovered printed prior art. A party may request reexamination, hoping to invalidate the patent or to confirm the validity of a patent. In other words, it is a process to reexamine a patent in light of a “substantial new question of patentability.”

Often, these requests arise in situations where a patent holder is or could be involved in a legal dispute.

EPX process

To begin the EPX process, a party files a request for reexamination during the period of a patent’s enforceability. According to the United States Patent and Trademark Office, the request must include:

    • A statement specifying questions of patentability
    • Detailed list and explanation of each claim to be reexamined
    • Copies of relevant patents and prior art or printed publication
    • Proof that the patent holder was served with notice of the request
    • Proof that the requester is allowed to seek reexamination

The requester must also include the filing fee, which could be $1,500, $3,000 or $6,000, depending on the entity size. This fee could be refunded, in some cases.

Upon submission of the complete information and fees, the examiners with the Central Reexam Unit will either deny or grant the request. If granted, examiners reexamine the patent with the owner of the patent.

Parties can expect a decision within two years. During this time, third party requesters will not be allowed to participate in the reexamination or amend the claims. The third party also may not appeal the decision, though the patent owner can.

If you are in a situation involving the question of patentability, this information can help you better assess your options. However, because intellectual property legal matters are often quite complex, it can also be wise to consult an attorney.


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