The U.S. Patent and Trademark Office keeps a searchable online database of issued patents and relevant information (Patent Application Information, or PAIR). There are three main factors that influence patent validity: term, maintenance fees and blocking patents, all of which can be found in the database. Sometimes, patents are declared invalid by courts, but unfortunately the Patent and Trademark Office does not keep records of these instances.
Go to the Patent Office’s online database and click on the “Public PAIR” link (see Resources).
Enter the patent, application, control, publication or PCT number into the text box and hit “search.”
Look at the filing date for the patent in question. All patents issued after 1995 have a term of 20 years from the filling date (designs have a 14-year term).
Look for any notes of extension on the patent, as some patents issued after 2000 have had terms adjusted. Extensions are noted with an asterisk.
Check the last page, as there is sometimes a certificate declaring that some of the patent claims are invalid.
Click on the “Fees” tab and click on the “Maintenance Fees” option. If fees have not been paid and the patent is invalid, the system will display an error message saying that the patent has expired.