How Long Does a Patent Last? by Joe Runge, Esq.

How Long Does a Patent Last?

To know how long your patent is going to last you have to know two things: what kind of patent you have and its earliest filing date. By understanding a few simple rules and the different kinds of patent applications, you, too, can reliably calculate patent expiration dates.

by Joe Runge, Esq.
updated July 13, 2021 ·  3min read

How long do patents last? may seem like a straightforward question, but it isn't. To answer it, you must first understand the different kinds of patents and some important dates in the patent process.

Step One: Know the Type of Patent

United States law provides for different kinds of patents. Each kind has a different duration. A design patent, for example, is valid for 14 or 15 years from the date the design patent is granted, depending on when it was filed.

When most people talk about patents, they are talking about utility patents. A utility patent protects processes, machines, or compositions. They are the most common kind of patent and are valid for 20 years from your earliest filing date. Determining the term of a patent gets complicated, however, if you have more than one filing date.

Step Two: Know Your Filing Date

To answer: how long is a patent good for, you need to know the date you filed the patent. Filing dates are recorded by the patent office and are part of the patent record on public databases. Every patent has a filing date.

Knowing your filing date is the first step to answering the question, How long is a patent valid? However, you can have more than one filing date.

The Provisional Patent Application

For example, if you file a provisional patent application before your utility patent application, you have two filing dates. A provisional patent application is an inexpensive way for an inventor to get an informal application on file. The term of a provisional patent application is one year. The provisional patent application is a mechanism that gives inventors an extra year to run experiments, find investors, or build a prototype. That extra year, however, comes at a cost.

If you are going to claim the benefit of your provisional patent application, the term of your patent starts on your earliest filing date: the provisional filing date. A utility application that claims the benefit to a provisional patent application will expire up to a year earlier. In return for having that extra year to work on your patent, you lose a year of patent life. So, how long does a patent last? Be sure you are calculating the term from the right date.

The Effect of Having a Patent Pending

Limited patent life is the cost of patent-pending status. Your first filing date drops anchor and your patent protection will only go for 20 years from that earliest filing date. That is why your first filing date is called your priority date.

There are other ways in which patent applications can claim priority to part or all of an earlier application, but all of them come at a cost of a shorter patent term. Keep in mind that you will not have enforceable rights for the full duration of your patent term. You cannot enforce a patent until the patent office allows claims and issues a patent for your invention.

If due to the fault of the patent office, there is a substantial delay in getting your patent claims, then you can have the time of the delay added on to the length of your patent. This process is called patent term extension and it occurs due to a delay in a response from the examiner or from the application's sitting in line for a long time before prosecution.

It Also Matters When You Filed

When you file your patent application also influences how long your patent lasts. For utility patent applications filed on or before June 8, 1995, you calculate the patent term differently. The patent expires 17 years from the date that claims issue. On June 8, 1995, laws went into effect that changed the term to bring United States patent law in line with the rest of the world.

A similar change for design patents occurred more recently. For design patent applications filed on or after May 13, 2015, the term is 15 years from the date that claims are granted to the inventor. Before that date, the term was 14 years from the date that claims were granted.

Knowing how long your patent lasts depends on what kind of patent you have and when you filed it. The rules can be complex, but the underlying law is straightforward. As long as you know when the laws changed, just remember that the earlier you get your invention on file, the sooner your patent will expire.

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Joe Runge, Esq.

About the Author

Joe Runge, Esq.

Joe Runge graduated from the University of Iowa with a Juris doctorate and a master of science in molecular evolution. H… Read more

This portion of the site is for informational purposes only. The content is not legal advice. The statements and opinions are the expression of the author, not LegalZoom, and have not been evaluated by LegalZoom for accuracy, completeness, or changes in the law.