The general rule is that the term of a patent is 20 years upon filing or 17 years upon issuance depending on the date that it was filed and whether it was enforceable on June 8, 1995. The term may be adjusted to account for delays caused by the Applicant or the Patent Office. If the patent is the second patent in a family of patents, then the patent term is calculated from the first filed patent application except that the filing date of a provisional patent application is not used. A patent’s period of enforceability can be cut short if the patentee fails to pay regular maintenance fees. Moreover, the patent term or the period in which you can enforce your patent does not start until your patent application issues as a patent. There are many different exceptions to the twenty year upon filing rule. As such, please consult a competent attorney to determine whether your patent or a competitor’s patent is enforceable.
You may also be interested in Adjusting Patent Term Due to Delays.