Patent citation

Any discussion of patent citations begins with a root document². WIPO's guidelines for patent landscape reports define the two directions from that starting point².

Forward citation counts need care. Citations are based on discrete documents, so a recent granted patent may have no forward citations while its corresponding pre-grant application has several. WIPO's guidance is to aggregate them across the family members the document represents, and to separate citations from the assignee itself from those of other organizations².

During prosecution an examiner looks for prior art related to novelty, obviousness or inventive step. References of this nature are cited in the document at different publication stages, usually within a search report that accompanies it². An applicant may also refer to other patents and to journal articles in the description of an application¹.

• US examiners. During examination the examiner should cite appropriate prior art nearest to the subject matter defined in the claims, and its pertinence should be explained (MPEP 707.05)³.
• Where they are recorded. The examiner places the identifying data of references cited for the first time on form PTO-892, Notice of References Cited, and no distinction is made between references on which a claim is rejected and those formerly referred to as pertinent (MPEP 707.05(c))³.
• Allowed applications. They should generally contain a citation of pertinent prior art for printing in the patent, even if no claim was considered unpatentable over it³.
• Applicants' references. The examiner must consider all prior art references cited in the application, including those cited by the applicant in a properly submitted information disclosure statement³.
• International search reports. Applicants in PCT related national applications may cite the material citations from the PCT International Search Report by an information disclosure statement to ensure consideration by the US examiner³.

Each individual associated with the filing and prosecution of a US application has a duty of candor and good faith in dealing with the Office, which includes a duty to disclose all information known to that individual to be material to patentability (37 CFR 1.56)⁴.

• Who. Each inventor named in the application, each attorney or agent who prepares or prosecutes it, and every other person substantively involved in its preparation or prosecution who is associated with the inventor, the applicant, an assignee or anyone to whom there is an obligation to assign it⁴.
• What is material. Information that is not cumulative to information already of record and that either establishes, alone or with other information, a prima facie case of unpatentability of a claim, or refutes or is inconsistent with a position the applicant takes in opposing an argument of unpatentability or asserting an argument of patentability⁴.
• How long. The duty exists for each pending claim until the claim is cancelled or withdrawn from consideration, or the application becomes abandoned. There is no duty to submit information that is not material to the patentability of any existing claim⁴.
• Foreign counterparts. The Office encourages applicants to carefully examine prior art cited in search reports of a foreign patent office in a counterpart application⁴.
• Continuations-in-part. In a continuation-in-part the duty includes information material to patentability that became available between the filing date of the prior application and the filing date of the continuation-in-part⁴.
• Consequence. No patent will be granted on an application in connection with which fraud on the Office was practiced or attempted, or the duty of disclosure was violated through bad faith or intentional misconduct⁴.

Applicants submit information through an information disclosure statement (IDS). Whether the Office considers an IDS depends on when it is filed (37 CFR 1.97)^4,5:

• Under 37 CFR 1.98 the IDS must list all patents, publications, applications or other information submitted, with a column for the examiner's initials⁶.
• It must include a legible copy of each foreign patent and each publication, other than U.S. patents and U.S. patent application publications unless the Office requires them⁶.
• For each non-English document it must include a concise explanation of relevance, and a copy of any English translation that is within the applicant's possession, custody or control or readily available⁶.
• No extensions of time for filing an IDS are permitted under 37 CFR 1.136. An IDS that does not comply is placed in the file but will not be considered⁵.
• Filing an IDS is not a representation that a search has been made, and is not an admission that the information is material to patentability⁵.

At the EPO, every document cited in the search report is assigned to a category by placing a letter in the first column of the citation sheets. Categories can be combined if necessary¹¹. The EPO Guidelines (2026 edition) describe these categories among others^7,8,9,10,11.

WIPO's patent information module describes citations as an important tool for analyzing the research and development activities and technical trends of competitors¹. Its landscape guidelines add that studying citations helps identify seminal documents that could have had a high impact on the development of a technology². A citation shows a relationship between documents, not that the cited document defeats the claims of the citing one: in an EPO search report, for example, an A document is state of the art that does not prejudice novelty or inventive step⁸.