A patent can be reissued under a limited set of circumstances. Generally, if an error is discovered which renders the patent wholly or partly inoperative, reissue may be the vehicle to correct the error. The Patent Office will reissue the patent to correct the error. You must pay a fee to reissue an application, and you must agree to surrender the original patent being corrected; you cannot have two concurrent patents on the same invention. The term of the reissued patent is limited by the unexpired term of the original patent.
New matter cannot be introduced into a reissue, but the scope of the claims can be enlarged to include broader subject matter when filed within two years of the grant of the patent. This is a common reason to file a reissue. Other reasons include correcting inventorship or adding narrower claims that should have been incorporated into the original patent. Some things, however, cannot be cured with a reissue. For instance, if a divisional was not filed during the pendency of the original application (after a restriction requirement was made), a reissue cannot be used to file the claims that would have been in the divisional application. Somewhat similarly, a reissue cannot be used to “recapture” claimed subject matter which was canceled from the original application, because such subject matter is considered to have been surrendered to the public.