Generally, a patent will be enforceable beginning on the date it is issued by the United States Patent and Trademark Office, and run for the length of its term, unless something causes it to expire earlier. Once the patent expires, the invention is now freely available to anyone, and no one can claim a new patent for the invention.
Everything you need to determine whether a patent is still in force is available on the USPTO website. You could also use Google Patents. Most patents will be viewable in text format, though for certain older patents you will only be able to view them by image, in PDF format.
The United States Patent and Trademark Office also now offers a Patent Term Calculator that can be downloaded and used to estimate patent expiry dates.
If a patent is an original-issue Utility Patent, not a Design Patent (number starts with “D” or “Des”) or a Plant Patent (number starts with “P” or “Plt”) or a Reissue of a Utility Patent (number starts with Re) and the patent number is 4,999,999 or less, forget about the search! All such patents have been expired since at least August 31, 2010. Your job is done!
The first step is to find the patent if you do not already have a printed copy. You can bring up the digital version on the United States Patent and Trademark Office patent database, the European Patent Office’s espacenet system or in Google Patents.
For Utility Patents and Plant Patents filed after June 8, 1995: These patents will usually have a term of 20 years from the US filing date of the earliest non-provisional application in the chain of parentage upon which the patent is based. See our Patent Timeline page for more information on how this timing works.
For Utility Patents and Plant Patents that were pending on June 8, 1995 and for any Utility or Plant Patents that were issued after June 7, 1978: If they haven't expired by June 8th, 1995, their term will either be 17 years from the date of issue or 20 years from the U.S filing date, whichever comes last.
For Utility and Plant Patents issued before June 7, 1978: a 17-year term measured from the date of issue. These will all have expired by now.
For Design Patents filed before May 13, 2015: 14-year term measured from the date of issue.
For Design patents filed on or after May 13, 2015: 15-year term measured from the date of issue.
Certain patents are tied to the expiry of earlier patents. Because of this, certain patents will have shorter terms than they might otherwise appear to have. This is called a “terminal disclaimer” and is the result of two applications that have claimed basically the same invention. Terminal disclaimers are usually marked on the later-issued patent and are sometimes flagged by an asterisk after the patent issue date, but sometimes they are marked differently. They may only appear in the text of the patent or with the “related application” data. In rare cases, there’s just a note printed on the patent that says, “This patent is subject to a terminal disclaimer” without any further information.
The best practice is to go to the United States Patent and Trademark Office Public PAIR system and find the terminal disclaimer itself in the Image File Wrapper. For older patents that do not have a File Wrapper, you can try looking on the “Continuity” tab or the list of related applications on the patent itself. If there is only one prior patent in the chain, you can be fairly confident that the terminal disclaimer refers to that patent. You can then look up that patent, go through the entire procedure to determine the expiration date for both patents.
Terminal disclaimers can affect a patent's term in a variety of ways:
In the recent years, the majority of terminal disclaimers referred to the “full statutory term” of the earlier patent. This would typically include the length of any term extension granted to the earlier patent. This is especially true if the terminal disclaimer refers to the term set by 35 USC 154, since the section both sets the term of the patent and determines an extension to the term for USPTO delays.
Before 1995, it was common for the terminal disclaimer to disclaim term past a stated date (“all term after March 3, 2013”) without referencing the term of any other patent. In these cases, the date sets the disclaimed term for the patent. This method is uncommon today.
Some older terminal disclaimers present both a date on which the earlier patent would normally expire as well as a disclaimer of the term of the earlier patent. The “specified date” is measured by the term of the earlier patent, even if that expiration date is later than the specific date given. These cases generally dealt with patents where the reason for the difference in the term of the base patent was:
This usually had to do with the June 1995 change from the 17-years-from-issue to 20-years-from-filing.
For patents filed on or after May 29, 2000: It is possible for these patents to have had their terms extended for Patent Office delays. These extensions are called "patent term adjustments” and are automatically given when the patent is issued. They are usually marked on the face of the patent, usually flagged with an asterisk “(*)”.
For patents issued between August 2009 and March 2010: According to the January 2010 Wyeth decision, the United States Patent and Trademark Office had been calculating the adjustments inaccurately in some cases for patents filed between August 2009 and March 2010. Those affected could apply for an adjustment, up til September 2, 2010. For those who did, the USPTO adjusted the term of the patent in case an error had been determined in the initial calculation. All of these patents should be new enough to have the Wyeth request form available in the USPTO’s Public PAIR system.
Special Cases: Extreme delays in the application process resulting from government action outside of the Patent Office can result in patents having their terms extended. This would include such things as regulatory delays, FDA approval, etc. These special extensions are almost never seen outside of the pharmaceutical industry, medical devices, and sometimes food products.
You can see the list of extended patents on the Patent and Trademark Office’s Extended Term List.
The Effect of Terminal Disclaimers on Term Extensions
You would find a note of this on a certificate attached to the patent image on the United States Patent and Trademark Office database. Often it is the last page in the image file.
Very rarely the Commissioner of Patents will withdraw an Issued patent. In these cases, the patents are usually not available on the USPTO database.
Maintenance fees are due at 3.5 years, 7.5 years and 11.5 years from the date of issue. If the fee is not paid during the year-long window or during the following 6 months grace period (with surcharge), then the patent will expire.
Note that patents based on applications filed before December 1980, were not subjected to the payments of maintenance fees. The vast majority of these patents have long since expired.
To determine if the maintenance fees have been settled, visit the USPTO’s Patent Application Information Retrieval (PAIR) system. You can also use the “Maintenance Statement” selections to confirm that a fee was settled, and how much was paid.
Note: If the delay in the payment of the fees was unintentional, a patent which expired for failure to pay maintenance fees can be revived. There is a definite risk that a patent that expired for non-payment of a maintenance fee may come back.
Plant or Design Patents
There are no maintenance fees due on Plant or Design Patents.
When a patent is declared invalid by a court, the patent becomes unenforceable. It can be difficult, however, to determine whether or not this is the case without access to legal databases such as Lexis, Westlaw on BNA USPQ.
For those with access to the databases, you can search for the patent number in reported court cases to know if the patent might have been mentioned in any case report.
With the case citation, you can search the case in the Public Access to Court Electronic Records (PACER) system. Google search can also be helpful to see if a reported case turns up.
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