Can you submit a claim for prior art after a patent is issued or can prior art be used to protect a business against patent infringement ?

  • What do you mean with prior art. I get the impression you use the word differently than common use for patents, i. e. publications that were availeble to the public before a certain patent application was filed. Could you clarify your question please?
    – zip
    Commented Mar 2, 2016 at 0:34

3 Answers 3


In the United States, anyone can place a written statement in the file of a patent at any time, even after the issuance of the patent, that discloses prior art that may be relevant to the enforceability of the patent. The written statement is merely placed in the file, the patent itself will not be directly affected.

37 CFR 1.501 Citation of prior art and written statements in patent files. (a) Information content of submission: At any time during the period of enforceability of a patent, any person may file a written submission with the Office under this section, which is directed to the following information: (1) Prior art consisting of patents or printed publications which the person making the submission believes to have a bearing on the patentability of any claim of the patent; or (2) Statements of the patent owner filed by the patent owner in a proceeding before a Federal court or the Office in which the patent owner took a position on the scope of any claim of the patent. Any statement submitted under this paragraph must be accompanied by any other documents, pleadings, or evidence from the proceeding in which the statement was filed that address the written statement, and such statement and accompanying information under this paragraph must be submitted in redacted form to exclude information subject to an applicable protective order. (3) Submissions under paragraph (a)(2) of this section must identify: (i) The forum and proceeding in which patent owner filed each statement; (ii) The specific papers and portions of the papers submitted that contain the statements; and (iii) How each statement submitted is a statement in which patent owner took a position on the scope of any claim in the patent.

However the US Patent Office will not make any finding of validity of the patent based on the written statement unless someone files for a reexamination of the patent, which requires additional paperwork and a fee. The written statement may be sufficient to discourage the enforcement of the patent, or provide evidence for someone else to reexamine or challenge the validity. Maybe. The Patent Office will consider reexamining the patent if someone files a request for reexamination and pays the appropriate fee. If the reexamination is successful then one or more the claims of the patent may be withdrawn.

37 CFR 1.510 Request for ex parte reexamination. (a) Any person may, at any time during the period of enforceability of a patent, file a request for an ex parte reexamination by the Office of any claim of the patent on the basis of prior art patents or printed publications cited under § 1.501, unless prohibited by 35 U.S.C. 315(e)(1) or 35 U.S.C. 325(e)(1). The request must be accompanied by the fee for requesting reexamination set in § 1.20(c)(1). (b) Any request for reexamination must include the following parts: (1) A statement pointing out each substantial new question of patentability based on prior patents and printed publications. (2) An identification of every claim for which reexamination is requested, and a detailed explanation of the pertinency and manner of applying the cited prior art to every claim for which reexamination is requested. For each statement of the patent owner and accompanying information submitted pursuant to § 1.501(a)(2) which is relied upon in the detailed explanation, the request must explain how that statement is being used to determine the proper meaning of a patent claim in connection with the prior art applied to that claim and how each relevant claim is being interpreted. If appropriate, the party requesting reexamination may also point out how claims distinguish over cited prior art. (3) A copy of every patent or printed publication relied upon or referred to in paragraph (b)(1) and (2) of this section accompanied by an English language translation of all the necessary and pertinent parts of any non-English language patent or printed publication. (4) A copy of the entire patent including the front face, drawings, and specification/claims (in double column format) for which reexamination is requested, and a copy of any disclaimer, certificate of correction, or reexamination certificate issued in the patent. All copies must have each page plainly written on only one side of a sheet of paper. (5) A certification that a copy of the request filed by a person other than the patent owner has been served in its entirety on the patent owner at the address as provided for in § 1.33(c). The name and address of the party served must be indicated. If service was not possible, a duplicate copy must be supplied to the Office. (6) A certification by the third party requester that the statutory estoppel provisions of 35 U.S.C. 315(e)(1) or 35 U.S.C. 325(e)(1) do not prohibit the requester from filing the ex parte reexamination request.

The fees for filing a request for reexamination range from $3000 to over $12,000. expensive but much less than litigation.


It is my understanding that once the patent is issued prior art can only be used in a court of law to invalidate an existing patent through due process of law.


If your business has used the patented method before the priority date of the patent, you can use this to protect yourself from infringement claims.

If that is not the case, several ways to attack a patent exist (opposition, ex-parte reexamination, inter parte reexamination, invalidity lawsuits).

Please clarify your question as to what you want to know about or ask a new question.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .