About Patents

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What is a patent?

A patent is an intellectual property right granted by the U.S. Patent and Trademark Office that gives a patent owner the right “to exclude others from making, using, offering for sale, or selling the invention throughout the United States or importing the invention into the United States” for a limited time in exchange for public disclosure of the invention when the patent is granted. The “invention” is set forth by a patent’s “claims” (described below), and individual claims of a patent or patent application may be challenged, as set forth below.

Basic information about patents and the process of applying for a patent can be found at the Inventor’s Resources webpage. Also you may find this video from the Federal Judicial Center helpful in explaining patents and the patenting process.

How can I find out more information about the patent and who is behind the demand?

You can search on the USPTO website or a commercial website for a specific patent number and then download a PDF copy of the patent. The Resources section of this website also lists PTO and other sites that can tell you who is listed as the registered owner of the owner and patent portfolio of the patent holder. You can also check Secretary of State records, your State Bar, the internet, and related sources for information about the entity or attorney sending letters.

How do I find out how long the patent will be in force?

In general, patents can stay in force for up to 20 years from the time of filing although the actual length of a patent’s life can vary depending on a variety of factors. More information about patent term, and an explanation of how to estimate whether a patent has expired, is available on the Patent Term Calculator webpage. Also, note that the claims of a patent can be invalidated by federal courts and/or the USPTO only prior to their expiration date.

What if the patent is expired?

Even if a patent is expired, the patent owner has six years from the expiration date to file a lawsuit in order to collect monetary damages for past infringement before the expiration date. More information about patent term, and an explanation of how to estimate whether a patent has expired, is available on the Patent Term Calculator webpage. Also, note that the claims of a patent can be invalidated by federal courts and/or the USPTO prior to their expiration, but not afterwards.

How can I tell whether or not I’m infringing?

To determine whether or not you are infringing a patent, for example in response to a demand letter or lawsuit , you or your attorney would need to compare a patent’s claims and the accused product, system, or process. To infringe a patent, the accused must perform each and every element of one or more of its claims, or actively encourage, sell or offer to sell a component that leads to another’s infringement. The best way to understand each claim is in light of the description provided through the patent (called the “specification”). A person knowledgeable in the technology should be able to read the specification and be able to tell how to make and use the invention.

The written record created when the USPTO examined the patent application, called the "prosecution history" or “file wrapper," provides further context for understanding the boundaries of the claims,  especially with respect to the closest “prior art.” Prior art consists of the references (books, articles, web pages and other information) that are publicly available before the date that the application was filed. For many patents, the prosecution history is available for free via the USPTO Public PAIR (Patent Application Information Retrieval) website. If the prosecution history is not available on Public PAIR, you may order it online on the USPTO website. A registered patent attorney or patent agent can advise you regarding all of the above.

How can I tell whether the patent is valid?

An invention must meet certain threshold criteria of novelty, usefulness and nonobviousness in order to be patented.  You may challenge the claims in a patent (or patent application) by showing they should not have been granted, or should not be granted, if these criteria are not met. 

For example, the USPTO or a court may conclude that a claim in a patent or application is invalid if the claimed invention was disclosed, for example, in a prior patent or patents, a book, a magazine, a newspaper, a television show or movie, a webpage or other published work before the date of the claimed invention. Even if there are no such publications, a court may conclude that a patent claim is not valid if it is shown by other evidence that the claimed invention was offered for sale in this country or was disclosed to the public before the application for patent was filed. In addition, a court could find the patent invalid because it does not meet other statutory requirements, such as a sufficient written description of the invention, or because it does not describe subject matter that is patentable.  Finally, a court could find that the patent is unenforceable because of wrongdoing by the applicant, such as by defrauding the USPTO.

How can I challenge a patent?

If you have reason to believe that the patent is not valid or otherwise enforceable, there are several ways to challenge it:

  • You can challenge a patent application by submitting what is termed “prior art” (e.g., references, publications, or descriptions of the disclosures described above made prior to the filing date of the application) to the USPTO. This must be done before the patent issues. You can search for prior art on your own or by “crowdsourcing”, that is using an online community to assist with the searching. You can find a patent search “crowdsourcing” websites by performing an internet search. For more information about submitting prior art relevant to a pending patent application (rather than patent), please see our webpage on pre-issuance submissions.
  • Once the patent has issued, you can challenge it at the USPTO by filing a request for reexamination of the patent, or by filing an inter partes dispute such as a request for post grant review, inter partes review, or, for certain kinds of financial services patents, a covered business method patent review.
  • You can challenge a patent in court, either when defending yourself in a lawsuit brought against you for patent infringement, or by filing a declaratory judgment (DJ) action requesting the court to hold the patent invalid.

A patent attorney can help advise you about the various options available to challenge patents and patent applications. Please see the section “Do I need an attorney?” for further information.

Links Referenced on This Page:

Glossary of Patent Terms

Inter partes dispute

Inventor Resources

Federal Judicial Center Video

Patent Term Calculator


Search Patents

Pre-issuance submissions


Public Pair

The information presented on this site does not constitute legal advice. It should not be considered to replace advice from an attorney. Reference to any specific organizations, attorneys, law firms, corporations, or websites does not constitute endorsement, recommendation, or favoring by the USPTO.

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