Once a patent is issued, a patentee may correct a patent through any one of five methods:
  • Re-examination
  • Reissue
  • Certificate of correction
  • Disclaimer
  • Special petition to waive the rules
Re-examination is a process for correcting a patent that has issued when there is a substantial question of patentabilty regarding the scope of the claims. There are two types of re-examination proceedings: ex parte (single party) or inter partes (multi party). A request for re-examination must be based upon written references, and it can be initiated by anyone.

Reissue is a process for correcting a defective patent. A request to reissue a patent, unlike a request for reexamination, can only be filed by the applicant or the assignee.

A certificate of correction can be issued to correct clerical errors.

A disclaimer is a complete forfeiture of one or more claims or a portion of a patent term.

A patentee may file a special petition to have the commissioner waive the rules. This technique is rarely used.