A mistake of a clerical or typographical nature in an issued patent may be corrected by a Certificate of Correction (COC). Correction of the mistake may not contain new matter nor require reexamination. 35 U.S.C. 255. Furthermore, the mistake must have been committed in good faith. Id. If the mistake is that of the Patent Office, no fees are required to file the COC. If the mistake is that of an applicant, a fee is charged for filing the COC. In an effort to reduce the overall time required in processing and granting COC requests, the Patent Office offers an expedited method for obtaining a COC in which the patentee is required to show that the error is attributable solely to the Patent Office.
A patentee who discovers the inventorship of an issued patent is in error and that the error occurred without deceptive intent can have the Patent Office correct the inventorship by a COC. However, this kind of certificate is different from the kind used to correct minor errors in that proof of the facts must be submitted. 35 U.S.C. 256. Also, failure to claim priority can be corrected by a COC, provided a proper claim was made in a parent application. 37 C.F.R. 1.78.
Each issue of the Official Gazette (patents section) numerically lists all U.S. patents having COCs. The COCs are categorized by the week in which they granted. The list also can be found at http://www.uspto.gov/web/patents/certofcorrect.
According to Dennis Crouch, an associate professor of law at Missouri School of Law, the Patent Office has issued around 25,000 COCs each year since 2001. On a per patent basis, Crouch estimates about 15% of issued patents are associated with a COC. The graph demonstrates how the number of COCs issued by the patent office has spiked in the past several years. In response to the increase in the number of COCs, a number of automated and out-sourcing services have emerged to check issued patents for printing and other typographical errors.